Apple Mail IMAP Errors Again

Just started getting the following after opening the Desktop Client under my iCloud Email:

[IMAP] SERVER ERROR: invalid result 9 for UID SEARCH UID 7:8

Nothing of any usefulness concerning this error that I can find and Googling is useless as usual, so wouldn’t appear to be a common error. Happens even after closing down Client, ignoring error, so nothing else I can think of.