The bug is certainly annoying and I was very happy to see that it was in the 3.1 patch notes as fixed. Unfortunately I am still getting the bug as well. (PS5)
There is a workaround but its a pain in the * to do each time. I have to do it about 80-90% of the games I load into.
If you load in and see your load outs aren't there. Redeploy (or do this quickly before the deploy timer counts down - your call) then go to the menu then loadouts then click add new loadout, back out of the menu then go back in, select your specialist and you should have a new load out (just one) then you can edit that load out for the game so you dont get stuck with the default weapon for the whole game.
PLEASE FIX THIS ASAP DICE, really dont want to be doing this for another couple of months while you are on break. Yes the game shipped in a terrible state, but these fixes have come out much faster than the previous titles. That is appreciated.