A simple error was causing robots to crash the game if you encountered and destroyed them in an alien ship.
I have fixed the issue and tested it to confirm it is working as intended, as demonstrated in the following screenshots:
I encountered this robot in the depths of the UFO...
I managed to destroy it, with no crash...
Along with this one...
And this one...
This is unrelated to the issue with bipedal aliens, which still might cause an error. However, as far as I am aware that error does not crash the game, but simply disables the alien, causing it to freeze and stop reacting to the player.