I have the exact same problem as the OP: 2x rundll32.exe prompts after boot (and none after clicking Yes to both, until the next boot). I first noticed it around this time, last month. The PC restarted (it may have installed some windows updates at the same time, not sure), and ever since then I get these 2 prompts. If I give admin rights to Fences, I get even more UAC prompts every few minutes for things like automatic backups, trim logs, etc.
- C:\Windows\System32\rundll32.exe file has the yellow and blue shield
- Fences installed by default in C:\Program Files (x86)\Stardock\Fences. Only 'uninstall.exe' has the blue and yellow shield icon
- Fences.exe - Compatibility - 'Run as Admin' is unchecked
- 2x enabled entries for Fences Settings in Task Manager - Start-up
- Configure Fences - Basic Options - 'Enable Fences' is checked
- purged fences (as per the tutorial) and clean reinstall - no improvements
- automatic layout - no improvements
- sfc /scannow - no problems
Running Fences Pro (188.8.131.52) on Windows 10 (18362.592) + Windows Defender and Malwarebytes free (184.108.40.206) - all of them up to date. UAC is on default (level 3) setting (and I need to keep it this way because other people have access to this PC). I'm only using local accounts on this PC, and my personal account belongs only to one group: Administrators. The other accounts are members of Users or Guests.
I also run something else which changes how Windows works: DisplayFusion Pro. It is quite heavy, but also fixes many retarded 'features' in Windows. However, DisplayFusion has never triggered UAC apart from when it installs/updates.
I did not try the repair installation yet, but I wouldn't be surprised if it works (at least temporarily, until microsoft go and do what they usually do).
I think @emerysteele raised a good point about the blue and yellow shield on rundll32.exe; is there any way that Fences can go around this? Relying on microsoft to fix this permission issue and not continuously break it and everything else with every other update seems unrealistic.
I mentioned DisplayFusion earlier because they also seem to heavily rely on the same rundll32.exe, yet UAC never moans about it. Perhaps they do something differently that Fences could also look to implement and futureproof itself against.. windows.