Even if it unfortunately does not solve @boarim s problem (MTE does not run on the 6a and therefore cannot cause the described error), I wanted to post this briefly, since the MTE bug was mentioned here before.
I had the same issues described by miles992 when MTE was introduced.
When the app crashed, this always led to disconnections when "block connections without VPN" was enabled. Disabling MTE for Proton VPN helped as a workaround. Reading this discussion, i thought that something might have changed in the meantime.
And that's the case: I'm using the current version of Proton VPN (4.9.40.0) and have had MTE enabled again for this app for a few hours now - the bug seems to be fixed, I haven't had any connection drops or crash reports since then.