Error message from sdd

I’m getting a few of the lines pasted below in my daily logwatch report and I can’t find anything that seems relevant. The disk involved is a WD 1Tb sdd and is a member of a RAID cluster md127 and also md125. It has no non-md partitions on it. Is this message important and what does it imply? smartctl doesn’t show any problems with the disk.

/dev/sdd [SAT], is back in IDLE mode, resuming checks (1 check skipped) : 1 time(s)