Kicked from match. "The client failed the anti-cheat backend check". Got BANNED

I was in the middle of shooting in Big TDM mode and got kicked to the opening screen where error said "The client failed the anti-cheat backend check". But still can get to lobby. But when press ready got kicked again to opening screen with the same error message. I close the game and open it back. Still the same when I press ready.

I restarted my pc and works like usual. But it happens again on 2nd match. In Gun-Run mode I was also in the middle of shooting and got kicked out with the same "The client failed the anti-cheat backend check". I clicked OK again and got me to lobby again and got abandon penalty for I don't remember, like 5 minutes?

I get over it and watch YouTube instead while waiting for my abandon penalty which didn't caused by me quitting. After some time on YouTube, I alt+tab to the game in the opening screen the game said "this client's game account has been banned". I said "what?", "How?". How can I never have cheating got ban? I even reporting when I see a cheater.

Thankfully I screenshotted both error message and ban message. Please refer to the attachment.

Please do something, I don't want my account get banned. I don't want to lose my 4 years progression, skins, stats, Mirage Heirloom, and money I've spent on this game.

Additional suggestion. Please allow players to report wallhack because there's no option in the report menu. People can still just wallhack without using aimbot.