I had this issue and tried to dig around /etc/rc*.d/ and find / |grep -E "icon|thumb", but could not find any process that could be run, no daemon already there waiting for its time to recheck/sync icons. I couldn't see how rebooting was supposed to fix this if I couldn't easily find it in /etc/rc*.d/. Admittedly I was just digging around via the phone itself and that's a tad slow and painful. I didn't have the time (I have young kids), to ssh in from a comfy desktop and find it.

I rebooted, but I would like to know what command to run to fix this next time. I don't reboot my unix servers lightly.