Hi
I was testing a propeller plane on Eve utilizing the whirllgig turboprop engine, it worked fine, which made me realize an oversight.
Since the turboprop uses liquid-fuel, it utilizing combustion, since it uses combustion, it needs oxidizer. The propeller gets the oxidizer from the air but it's somehow working on Eve despite the un-oxygenated atmosphere.
It was a bug caused by another mod, apologies.