Michael,
You wrote that your gateway always bounces the first message from unknown mail servers.? IMO, this is a really BAD idea.? But anyway, it shouldn't matter, because by now your gateway knows about Groups.io (you have been receiving their messages for many months), so no more messages would be bounced.
When a message from Groups.io bounces, it registers as a "bounce" and does not unsubscribe you.? Bounces are tracked separately.? I see that you have no "bounce" messages any time in the last several months, so anyway that is not happening.
The changes to your Groups.io account are happening because someone (you?) is logging into your Groups.io account and making changes.
PLEASE DO THIS -->? Login to your Groups.io account now, and CHANGE YOUR PASSWORD ASAP.? Just in case someone else knows your password and is making changes on your behalf.
I guess maybe you have 4 accounts on Groups.io?? At least 3.? I don't know what the other *@*.de one is.? I guess that's the one you use for private email, not the one you're using now.
Andy
