Thanks for your answers.
I've been using BAM! for quite a while now (in fact, some years) without any problems other than having to deal with
a) Boinc Managers that are too old,
For a) the problem is that the older Boinc clients don't act on the features that BAM! uses as originally intended by Boinc, so the only preference BAM! propagates that I can use properly is the default one. For all newer Boinc Clients I can have other preferences, so I use one for each machine and the default one only for my Debian system that uses Boinc version 7.6.33.
Talking about b) now, Einstein went to ignore my generic, home, school and work preferences some weeks ago. This wasn't the first time they sent me work for Nvidia GPUs or CPUs although I had told the server to only give me AMD GPU work, and now I posted this on their forums as this repeatedly happened. One of the moderators told me it might have been some other project's or BAM!'s fault, but then a fellow cruncher added that this behavior might occur due to killed preferences. I investigated this (well, I had a look at my preference pages) and saw that this was the same that seemed to have happened to my prefs, as they disappeared after saving them - again and again. While I did not receive a message that there were no preferences for the generic set of prefs the settings also changed themselves.
Now I'm here, and my home, school and work preferences are gone although it was no problem to use them since about the beginning of this year.
On BAM! I don't use home, school and work prefs, only the default set and sets for each machine that are called after each machine and did not temper with home, school and work on this project.
To me this seemed to occur only after Einstein again messed with my prefs.
Thanks for reading.