It seems that sandbags are impervious to all explosive damage now. I just had a game where an enemy spawn point, well surrounded and protected by three sandbags, stood indestructible against multiple tnt packs and arty strikes, and the only solution was to dismantle it manually. I did some testing in the shooting range and neither ap/he ammo from tank guns nor bombs/rockets can do anything to sandbags. On the other hand, barbwires still function normally and can be destroyed by explosions.
I don’t know when this change to sandbags was implemented but I never had any trouble with sandbags before, granted that I do play this game way less now. This is definitely not right.