I have the same issue, in previous versions what used to take seconds now takes many minutes.
I am running the game in 3440x1440, borderless full screen. Same as in previous version
I can deploy all soldiers ( no MARS ) and go through the first round, then when the enemies have their first go the game locks solid
Attached end of first round save
auto_groundcombat_turn_1_end-3.json
Game locks up after first action.
Placed solders started combat and managed to get first soldier to fire then nothing part from able to move soldiers.
auto_groundcombat_turn_1_start-6.json
Probably part of the MARS bug as well.....