The crash is almost certainly that y'all ran out of tiles: there is a hard limit of 255 of them. I think that using Alien Biomes (default settings) and Asphalt Roads at the same time uses ~ 235 or 240 of them, so you add a couple more mod tiles and you run out.
When you go over the limit Alien Biomes logs a warning in the factorio log, but there is no other information. Tiles over 255 just don't exist in the game, so if some of the asphalt tiles were cut ... you would just find they don't exist.
Anyway, check the factorio log to see if that happened.