In my case I tried to put a loaded (capped) ram on a transport ship in the first scenario of the Joan of Arc campaign and twice the game immediately crashed as soon as I put the ram on the ship - only the second time I realised what caused the crash. Didn’t happen again with an empty ram when I tried for the third time.
Furthermore, I tried with every type of ram. I noticed though that it only happens when “careening” is researched. Without that technology it seems to work fine.
Start any game (doesn’t matter if said campaign or standard singleplayer game)
Load any type of ram with any amount of units (I tried with different amounts of foot soldiers)
Put the loaded ram on a transport ship with careening researched and the game will immediately crash, as if I pressed Alt + F4. (there is no crash report either)
Oh, then this bug is much worse than I would’ve thought. I never noticed that the AI puts loaded rams so frequently on transports, apparently. I guess most players don’t even know that that is a possibility.