Apparently the Braindead achievement is still bugged after the patch, contrary to what changelog says.
Can you please check its functioning again? Thank you!

I received this achievement a few days ago. This last patch is normal.

Hi, thank you for your reply! Maybe I do something wrong, can you tell me exactly what have you done to complete it?
I tried with the last mission of the original campaign. I pressed Alt-Tab a pair of time, maybe is this that broke the achievement.

Hi, I received this achievement as soon as the credits began (after the last patch). I think this was remembered in the statistics of the game and I got it quickly. I tried different ways to get it before: I played the level many times, spent about two hours on the credits, pressed Alt-Tab (and did not press) So now I can not say exactly what I did right to get it

You will have to try different ways, I suspect that you will have to replay level40 many times and watch titles again and again(but it is not exactly)

Sorry for my English

P.S. And do not forget to enable the option: run the game in the background

I have done all these things, but for some reason I'm still unable to unlock it, I'll try to contact the support, maybe they can do something, thanks for help anyways!

Try to contact support, but I already did it. They checked the achievement three months and wrote that it is now working!