I use bin 2 for guiding with an ASI174MM Mini camera. Latest KStars (3.7.0 from Ubuntu PPA) resets this setting to 1 on each new session most of the time. I have to change it to 2 manually each time. A couple of times it actually started with 2 on its own. I have no idea how those sessions were different from others.
Several older versions worked fine in this regard.
Tell me if you need any particular verbose logs or files.

I want to confirm this! On KStars 3.7.1.beta (recent master) binning in guide module is not saved anymore and resets to default 1x1 for a new start.

Ok, seems there are some inconsistencies with the user database. Unfortunately I did not find the reason until now.
As a workaround one can delete the database and create a new one while starting KStars. However deleting the database means to lose all user settings! So just be sure to save the old database for security.

After a couple of restarts and some changes of guide parameters the binning issue is back. Even creating a totally new profile with new optical trains does not help to cure the guide binning issue. It seems that recent changes in the handling of UI parameters are provoking such issues (see also here ). Even if a new profile can help, it is not always a practical way. Especially if there are a lot of user settings you do not want to loose!

Is there somebody out there with similar problems?

A very strange occurrence is shown in the following video, where I create a profile from scratch and guide binning is consequently set back to 1x1: test.mp4

Unfortunately I did not yet receive some feedback, but I think a found a solution for this specific problem. I've uploaded a MR that addresses the guide binning problem. I suppose though other EKOS modules suffer from the same flaw. I will report more, when Jasem (or one of the main developers) confirms the MR.