Slitherine

In MP had a Highland unit that invaded Skyline. Fared poorly against AT guns trained on the entry area and FM broke. It "could not regroup" although the conditions in 18.14 were met:
1. ended due to FM failure
2. held one victory location (in the entry area, so should be an "exit vicotry location")
3. map entered from is friendly controlled with one BG in it, so should have room
4. lost all one victory locations held does I think satisfy the condition that all locations were lost due to force morale differential.

Without seeing the exact situation, it is difficult to say. Were you the host or the joining player in the multi-player game?

One condition not mentioned in the manual is that a BG with very low cohesion (less than 33%) cannot retreat. Was that a possibility in this case?

Steve