So, I have to concede about flashbangs vs sheevar being bugged it seems. I could successfully flashbang a few sheevars in 2.6. The sound does not always play though, depending on how I can see (or not see) the target, albeit it's still affected. For instance, I just flashbanged a Taman, it definitely worked, but the sound didn't play. Two times even. Probably because I had first discovered the Taman via infrared goggles, but could see him directly once the flashbang hit.
Normally sounds play even if the player doesn't know an enemy is there. The sounds also play at odd times...for instance, if I have units in smoke and some other unit (not in smoke) uses the infrared glasses, the units in smoke cry because of suffocation. Need to check whether they really suffocate or just cry.
So, there are some bugs here.
problem: Oftentimes the target unit is standing facing a wall, is it still possible to flashbang if it lands on its spot ?