After some more research, we came to the conclusion that it is not related to Chromium Embedded Framework.
However, having more users reporting this issue we have reason to believe that this issue is related to a recent bug in Bitdefender: https://community.bitdefender.com/en/discussion/89709/out-of-memory-error
It appears that in a recent December update, Bitdefender causes itself and other apps to use up most of the system's memory, which results in Apps like Boxcryptor to fail with
OutOfMemory errors at some point.
To overcome this issue, it is recommended to either uninstall Bitdefender or, if applicable, disable Advanced Thread Defense and then to restart the affected device.
If you run into these issues without having Bitdefender installed, please let us know, too!
Edit: Note that we are in contact with Bitdefender Support and will let you know as soon as we have an update from their side.