Unity automatic UI navigation events get messed up after entering playmode

When in Editor, automatic navigation of selectables looks reasonable. When I enter play mode it changes to the point, some of the buttons are unrechable!

Why does it recalculate it differently? I disabled all other game objects, canvases, etc - I have only this menu that consists of various layout groups and it still messes up the navigation.

Can I somehow debug the calculaton Unity perfrms? Check why it picks such paths? If I would know how it works under the hood I would probably be able to adjust to Unity's expectations.

I use Unity 2020.3.28f1 LTS

I know I can force an explicit navigation, but it kinda defies the idea of having an automatic option. Thanks for any suggestions!