Another little bug. When swapping engine from carbon to steam engine (with rockets modules built on it), the engine become unselectable. Then u can see in this picture the strange thing happening when i try to build a new engine. I had to reload then deconstruct the engine and rebuild anew (same bug behavior as the payload unselectable bug, reloading solves the issue).
May be this is caused by the gas port of the steam engine potentially overlaping with a bridge. I didnt retry deconstructing it before though.
Swap carbon engine with steam engine on rocket with modules.