I'm having the same problem, but not just with re-boots. Sometimes Windows 10 "hiccups" & it messes up my taskbar & fences. And yes, the icons leave the fences even though they're locked. Luckily restoring the snapshot fixes it, but it's really annoying. This has been going on for at least 3 months. My Windows 10 version is 20H2 (OS Build 19042.746). That's a recent update due to another problem with shared folders, which didn't work. I have Fences Version 126.96.36.199. Any help would be greatly appreciated.
Sorry to hear you are having issues. Please try purge and reinstall steps as mentioned here: https://forums.stardock.com/486084/fences-support-faq#reinstalling Just make sure to redownload the latest version from your account. Reboot after the purged. Reinstall, and Reboot again after the installation. Retest it. Report back here.
Stardock Community Assistant.