I believe I have the same problem though the symptoms are different the error messages seem the same.
In my case Boxcryptor works fine, but then just stops after several hours or even a couple of days.
This is happening on 2 W10 pcs both about 5 years old one intel and one AMD.
One is online account and one is local.
Looking at the w10 event log there is a .Net runtime error
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: exception code e0000008, exception address 76C3B522
This is followed by a Application Error
Faulting application name: Boxcryptor.exe, version: 2.49.1965.0, time stamp: 0x61657247
Faulting module name: KERNELBASE.dll, version: 10.0.19041.1415, time stamp: 0x2791d798
Exception code: 0xe0000008
Fault offset: 0x0012b522
Faulting process ID: 0x1c08
Faulting application start time: 0x01d7f7116094bc86
Faulting application path: C:\Program Files (x86)\Boxcryptor\Boxcryptor.exe
Faulting module path: C:\WINDOWS\System32\KERNELBASE.dll
Report ID: 06d65b97-4bd1-489c-a96e-6cfe23795823
Faulting package full name:
Faulting package-relative application ID:
I believe that I am running version 4.8.4084.0 of .NET
On one pc I have run >NET repair process and uninstalled and reinstalled Boxcryptor.
I think this may have started with the last W10 2021-12 update.
Sorry to raise this just before Christmas