Impalers head hitbox glitched?

Recently I've noticed that the exposed head weakpoint on impalers is eating through anti tank options like candy, the recoilless is taking anywhere from one to three shots to destroy its head when exposed, if I recall this part is only supposed to have an armor class of 2 with 1250hp, why is the recoilless with its 3000+ standard and durable damage not able to 1 shot it? The only times I've managed to get a 1 shot is when I aim for the small v shaped gap between it's tenticles, but even then it is highly irregular, and I don't seem to have this issue with hitting any other units weakpoint. Ive tried this with the quazar and the expendable as well they seem to have the same 1-3 shots to kill even though they have considerably lower damage per shot, any help or insight into what I may be doing wrong would be highly appreciated, thanks! I'm on ps5 if this helps.