Sounds like either a connection problem or that you have your V-Sync set to off.
The reason is that in all my time flying the Il2 it's only taken a max of two 37mm hits from an osty to kill me in one. I reguraly kill Il2's in a 110c but w/o the 30mm cannon it can take quite a few 20mm.
I haven't hit a plane w/ the panzer's cannon in a long time but I do remember that when I did the AP round against a bomber the round didn't do much visual damage, but the HE round was insta death for any plane it hit in the air or came close to on the ground.
Hope this helps, if you have your V-Sync already set to ON and a ping plot when you are having this type of issue doesn't show any problems then....nevermind.