The left arm on the MDD-B variant appears to be bugged. Placing it on my starting 'mech causes the weapons loadout to fail to load until I switch to and from another 'mech. Placing it on a starmate's mech bugs their AI so that they stand in place for the duration of the mission; while you can still move them manually if you switch to them, you cannot lock on with LRMs in that state. I suspect it has something to do with the hand actuator, which does not appear in the loadout and cannot be grouped; switching to a different left arm (MDD-Prime in my case) solved the issue.

I will let you know if I run into anything else. I'm really enjoying the mod otherwise!