[Mobhack]

So long as some crew is left, experience gain continues.

Losses are by the whole element, not by crew. So you need to have a unit totaly destroyed (no crew surviving) to revert to the start of the experience ladder.

If a unit is badly damaged in a battle, it tends to be more difficult for that element to gain experience.

If you change a unit to another type it can lose a few experience points for retraining on the new equipment.

Cheers
Andy