Using vanilla maps in game causes a game breaking bug around oil deposits and can potentially break your save as well preventing you from reloading the game whilst still having the map in hand.

Luckily, I was able to swap my held item whilst the game was loading but on my test world to recreate the problem, it broke again and I was unable to reload it.

I haven't tested how the vanilla maps handle other buildcraft entities but could be a similar problem.

can you please provide a crash log?

Already fixed in dev