I'm not sure if it's Firefox's VPN or the most recent Windows ESU or a combination of the two, but really weird things are happening when I reboot my system and it tries to enter windows via my local account.

I checked AI and it said yes it is highly probable that the combination of Windows ESU and the newly added Firefox VPN is causing your system to act weird. Recent Windows updates have been known to cause conflicts with VPN software, leading to network issues and system stability. I've turned off the VPN in Firefox and the VPN setting in Windows VPN Advanced Options today. I did notice my system appears to struggle when it hits the McAfee program when trying to load the Windows Desktop Screen.