Any suggestions on how to resolve? Except to withdraw?

I guess that depends on how they're stuck. Are they stuck on terrain? Are they just refusing to move at all? When you end turn, does the turn progression hang because they never take any action at all, even to end their turn?

Try moving yourself out of the way. If they're near where they spawned, maybe blow up a few buildings in case one of them is messing with pathfinding.

If that doesn't work, then just gather up your 'Mechs and run over to the extract point, see if you can spawn the reinforcements that usually show up on those missions, and see if that kickstarts the AI in the escorts.

If none of that works then I guess you should just reload the mission. :/

The issue is that 1 of the units where stuck on terrain... I tried posting a screenshot but size limit is just 2 mb and the screenshots are 5mb, and no bloody weblinks are allowed here..

My solution was to load a previous savegame...

None of my mechs where even close to the allied units...

You can post a link if you just cut the http://www off of the front.