Some distress signal helis being very difficult to take down/possible invulnerability glitch?

A player and their team did 6 distress signal helis today. Two of them seemed to be bugged, as it took way more than 100% damage to take them down. I did not witness it, but they said that after it was smoking, it stayed smoking for a few minutes and seemed to absorb a ton of bullets without taking further damage. I am wondering if there is some kind of possible invulnerability glitch where distress signal helis are absorbing bullets but not taking any damage. Combatlogs attached.