The phone you're seeing this on is running GrapheneOS, right? You haven't rooted your phone or kept your bootloader unlocked have you?
Maybe also try going in to the app's settings and clear the app's storage.
Based on what the lead dev said on Matrix and what I understand of the code, this kind of error shouldn't happen unless it's the multiple signatures thing that restarting fixes. The alternative is something is wrong with the app somehow.