Do you have Obtainium installed on another profile? App updates go to all profiles at once. You'd get an error if you may be installing an app you installed on another that is a version lower or if it has a different signing key. Make sure to use the latest APK/version.
Discussion
Yes. I just figured that a solution to my problem would be to remove the app from obtainium but not from the profile. That way, when the app is updated by google play in the other profile it also updates in the profile that has only obtainium. This way the errors no longer occur.