I found probability of ammo detonation of armoured vehicles might have been decreased from last major update, but today I found some of them might have been rolled back but some have not. (more information here https://forum.enlisted.net/t/did-probability-of-ammo-detonation-decrease/100516) Last time to find similar change is when High Calibre major update come out with some premium tank destroyers, probability of all tank destroyers have been decreased for several weeks.
I think balancing vehicles by frequently changing its performance related parameters are very irresponsible changes which make the game experience unstable and inconsistent. And moreover make these change without a changelog is disrespectful to players’ trust.
Really hope they stop this in the future, they should try only use battle rating to balance weapons and vehicles.