AFAIK almost everything about the way SM has implemented Python is broken. Each and every flavour of GUI has 'issues'... it's a case of pick your problem!

Without doing one program in each GUI and picking which fails less, which I couldn't be bothered doing, I picked Tkinter in 2009 and stuck with it. It works well enough for me so I am not too bothered it's a dead end tech.

I picked Tkinter because I began with P7 and it 'kinda' worked there while wxP was a distant unimplemented upstart.

They all have issues.

If it's not broken Threads, it's a half-*ssed or broken something else that works on PC doesn't on MAC or vice versa.

Not much to choose between them to be honest IMHO.

If something ever manages to work on a multitude of platforms, you can be sure it will be crippled by commercial interests, be bought up and destroyed, be unusable without a degree in Swahili and Urdu or become obsolete pretty soon!