Crabmen Quit Moving Partway Through Mission

After doing the Fort several times I decided to give the random map a shot. Everything was going well, I slowly lost my two assaults and sniper against the hordes (seriously, something like 12+ crabmen were on the map), and the queen was chasing me (the sniper was able to take out the pincers before getting ambushed by one of the gunners). But then something weird happened. While the queen kept chasing me the crabs just stopped. Well one of them kept going but even he wouldn’t fire. Instead all enemies would just auto end their turn. They didn’t throw grenades, didn’t fire, pincer crabs would just stand there and end their turn. It took awhile for me to clear out the rest of the map (had to clear out 7 crabmen with my Heavy alone) and not a single one moved or fired once the queen died. In fact I think one of them ended up resetting back to his original spawn since I saw him chase after me for a bit while the queen was chasing after me but once she died (she stood over me and I couldn’t move until she bled to death) he was no longer where I last spotted him and instead back at what appeared to be his original spawn point.