Getting message that shouldn't get and old ones

Good team, developer, gifted user,

since a while (some days) my person gets old till very old messages in chats which had been left long time ago, and from user having abound once delta-chat’s use.

My person thinks that there was currently a topic (German, if right) on maybe a similar issue, but didn’t find it in quick manner.

My person guesses that it might be in connection with re-use of DC by others who got somehow not informed about leave and maybe use newer versions now which seemingly work with other patterns.

Upgrade has stopped with version 1.38.2 on my side, since the “feeling” things run different since then.

I’m wondering: what are the exact things that prevent you from upgrading?

A ‘feeling’ that focus got astray, good master, which wasn’t that wrong soon later.
But my person is also usually not one who upgrades working things unless it could no more be used and seems still be given for good purposes.

On topic maybe: Could guesses, that primary patterns had been changed and might cause such ‘missunderstandings’ between versions, be right?

(‘please’ may good master be reminded that feed-forwards are never meant as demands but mainly just to bring things to attention for your and others good rolling on. Patient and care of yours are always worthy of appreciation.)