This bug is truly gamebreaking, because it makes Heat builds unplayable, as it is impossible to deal with kickback builds, when you can't use a hook+weapon or charge+weapon combo, as your turn ends after using the special every single time.

That's funny... both hook + weapon and charge + weapon is working fine for me, my turn doesn't end. Are you sure your mech isn't automatically cooling down leaving you with one turn?

After doing some stuff to improve PC performance, I've found the problem is special animation taking too much time on slower PCs.

Still something is not right, as there is no way the animation lasts 18 seconds, its more like ~10, and then turn ends. It's working fine for me now, so I guess it's up to the game devs if its worth it to fix the issue for slower pcs, to avoid losing those potential customers.

FWIW I think with all those animation using up turn time, a turn should last 30 and not 20 seconds. Also, 30 seconds tends to be pretty widely used timer length for such games.