I did this again (debug rpc, try mount, dmesg) which resulted in a somewhat different output.
The mount of the file system on oursecondserver is done via nfs v3, the one on ourserver is mounted via nfs v4.
[ 765.396319] NFS: sending MNT request for oursecondserver.ourdomain.org:/export/path
[ 765.398365] NFS: received 1 auth flavors
[ 765.398382] NFS: auth flavor[0]: 1
[ 765.398401] NFS: MNT request succeeded
[ 765.398402] NFS: attempting to use auth flavor 1
[ 765.399694] NFS call fsinfo
[ 765.399897] NFS reply fsinfo: 0
[ 765.399900] NFS call pathconf
[ 765.400096] NFS reply pathconf: 0
[ 765.400100] NFS call getattr
[ 765.400315] NFS reply getattr: 0
[ 765.400317] Server FSID: 65c3c268e5dab2ca:0
[ 765.400583] do_proc_get_root: call fsinfo
[ 765.400793] do_proc_get_root: reply fsinfo: 0
[ 765.400982] do_proc_get_root: reply getattr: 0
[ 765.400996] NFS: nfs_fhget(0:42/16895408 fh_crc=0x478ae16e ct=1)
[ 765.403083] NFS: revalidating (0:42/16895408)
[ 765.403089] NFS call getattr
[ 765.403472] NFS reply getattr: 0
[ 765.403476] NFS: nfs_update_inode(0:42/16895408 fh_crc=0x478ae16e ct=2 info=0x27e7f)
[ 765.403489] NFS: (0:42/16895408) revalidation complete
[ 765.403491] NFS: nfs_weak_revalidate: inode 16895408 is valid
[ 765.403495] NFS call access
[ 765.403830] NFS: nfs_update_inode(0:42/16895408 fh_crc=0x478ae16e ct=2 info=0x27e7f)
[ 765.403835] NFS reply access: 0
[ 765.403837] NFS: permission(0:42/16895408), mask=0x24, res=0
[ 765.403840] NFS: open dir(/)
[ 765.403873] NFS: readdir(/) starting at cookie 0
[ 765.403882] NFS call readdirplus 0
[ 765.404188] NFS: nfs_update_inode(0:42/16895408 fh_crc=0x478ae16e ct=2 info=0x27e7f)
[ 765.404193] NFS reply readdirplus: 652
[ 765.404203] NFS: nfs_fhget(0:42/33644731 fh_crc=0x97693b95 ct=1)
[ 765.404206] NFS: dentry_delete(/bin, 20080c)
[ 765.404210] NFS: nfs_fhget(0:42/51149943 fh_crc=0x93fa5bdb ct=1)
[ 765.404212] NFS: dentry_delete(/src, 20080c)
[ 765.404215] NFS: nfs_do_filldir() filling ended @ cookie 512
[ 765.404217] NFS: readdir(/) returns 0
[ 765.404225] NFS: permission(0:42/16895408), mask=0x81, res=0
[ 765.404230] NFS: dentry_delete(/bin, 28080c)
[ 765.404235] NFS: permission(0:42/16895408), mask=0x81, res=0
[ 765.404240] NFS: dentry_delete(/bin, 28084c)
[ 765.404244] NFS: permission(0:42/16895408), mask=0x81, res=0
[ 765.404246] NFS call getacl
[ 765.404498] NFS reply getacl: 0
[ 765.404500] NFS: nfs_update_inode(0:42/33644731 fh_crc=0x97693b95 ct=1 info=0x27e7f)
[ 765.404503] NFS: dentry_delete(/bin, 28084c)
[ 765.404507] NFS: permission(0:42/16895408), mask=0x81, res=0
[ 765.404510] NFS: dentry_delete(/bin, 28084c)
[ 765.404521] NFS: permission(0:42/16895408), mask=0x81, res=0
[ 765.404523] NFS: dentry_delete(/src, 28080c)
[ 765.404527] NFS: permission(0:42/16895408), mask=0x81, res=0
[ 765.404529] NFS call getacl
[ 765.404758] NFS reply getacl: 0
[ 765.404760] NFS: nfs_update_inode(0:42/51149943 fh_crc=0x93fa5bdb ct=1 info=0x27e7f)
[ 765.404763] NFS: dentry_delete(/src, 28084c)
[ 765.404767] NFS: permission(0:42/16895408), mask=0x81, res=0
[ 765.404769] NFS: dentry_delete(/src, 28084c)
[ 765.404773] NFS: readdir(/) starting at cookie 512
[ 765.404783] NFS: readdir(/) returns 0
[ 765.417529] Key type dns_resolver registered
[ 765.611426] NFS: Registering the id_resolver key type
[ 765.611437] Key type id_resolver registered
[ 765.611439] Key type id_legacy registered
[ 765.612209] --> nfs4_try_get_tree()
[ 765.618213] nfs_callback_create_svc: service created
[ 765.618219] NFS: create per-net callback data; net=f0000000
[ 765.618285] nfs_callback_up: service started
[ 765.618287] NFS: nfs4_discover_server_trunking: testing 'ourserver.ourdomain.org'
[ 765.746186] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 765.746194] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 765.746195] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 766.750060] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 766.750073] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 766.750080] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 766.750083] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 767.774065] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 767.774076] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 767.774081] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 767.774085] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 768.798084] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 768.798098] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 768.798105] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 768.798109] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 769.822102] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 769.822109] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 769.822113] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 769.822115] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 770.846108] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 770.846122] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 770.846128] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 770.846132] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 771.870119] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 771.870129] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 771.870134] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 771.870137] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 772.894140] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 772.894149] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 772.894153] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 772.894155] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 773.918141] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 773.918154] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 773.918160] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 773.918164] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 774.942143] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 774.942152] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 774.942157] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 774.942161] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16
[ 775.966164] nfs4_handle_reclaim_lease_error: handled error -10008 for server ourserver.ourdomain.org
[ 775.966178] --> nfs4_proc_create_session clp=00000000d4a0c6ba session=00000000e4767ae4
[ 775.966184] nfs4_init_channel_attrs: Fore Channel : max_rqst_sz=1049620 max_resp_sz=1049480 max_ops=8 max_reqs=64
[ 775.966188] nfs4_init_channel_attrs: Back Channel : max_rqst_sz=4096 max_resp_sz=4096 max_resp_sz_cached=0 max_ops=2 max_reqs=16