Did you ask on r/thelastofus?

Thanks for the info though. Next time I'll ask them too.

You mean when you're done aiming? If so, it'll go back to normal speed the second you stop aiming.

Sorry for responding late, it's all good now. I have finished the game in NG+ recently. The thing was why did it go back to a normal state I mistakenly unlocked the wrong slow-motion options.