Maintaining gtk2 is a lot of work, as there are code incompatibilities (beyond the GUI) between the gtk3 / gtK2 versions. I spent more than a day to find out why, exactely the same code (in rtengine) worked perfectly in gtk2 and ended up crashing in gtk3.
I asked the question a few days ago to know what was done with the various versions (2 and 3), it was chosen the "dev" branch (which is gtk3).
It would take a real request for me to rebuild gtk2, probably about ten hours (or more) of work, to run (without bug or crash) in the 2 environments. But of course, if necessary I would do it
It is important to specify which tool is used (color and light, denoise, etc.), I think that, if there is bug, it is a problem of dynamic refreshment
And thank you for testing, and thank you for all