MobX v6 with Expo SDK40

Have trouble in finding a working configuration with Expo SDK40 (managed workflow) with TS enabled and MobX v6 (i.e. latest, without decorators). MobX config ( requires changing Babel version from Expo SDK40 recommended 7.9 to 7.12 and adding one plugin ["@babel/plugin-proposal-class-properties", { "loose": false }]. When I do that my Expo app worked for a while until I added Stack Navigator into my react-navigation setup, then app would crash (only on iOS) when trying to navigate the stack.

After some googling found proposals for playing with Babel-config and after trying numerous suggestions & combinations only got app working when removed that extra Babel-plugin. Which then caused some trouble for MobX, but with some workarounds it seems to be mostly working…

Anyone else using this Expo + MobX v6 and has figured out the config for Babel?