Yeah, I do check for the existence of the covers & thumbnails in kfmon, so if the files are already there, it'd *probably* not fare much better. The only additional check is the db being locked, which might save the day (or not, due to the potentially huge timing variances).
But all that's moot anyway if the weird nickel restarting behavior also/still happens under KSM (which is something I think nobody has been brave enough to try, with good reason. If it's broke with only KOReader, I wouldn't even begin to imagine how much worse it could be with KSM
).