When Additional armor is hit, they are technically broken and disappeared(when broken, next shell directly hits main tank armor). but visually, they look still attached on the tank. And also non-armor structures like lights, trunks can be broken, but not that well.
This problem still appears after I redownloaded the game.
You can bug report it here (just search a bit first so that you don’t report something that is already reported and known about): (Gaijin.net // Issues)
A guide on how to report bugs can be found here: ([Navigation] Technical Knowledge Base | War Thunder Wiki)