When using PC and Xbox controller the brakes tend to get stuck on full service when trying to release them. It seems that when you have a lot of things to handle, the game is slow. If I compare the Class 101 Cornwall the 101 Tees Valley, the latter releases the brakes faster. Brake release issue also on the 150.
I’ve read that others are finding a conflict between controller and keyboard used at the same time on pc that is slowing things down. Try without controller and see if it resolves. I’m speaking second hand as I’m on console, but for the record keyboard and controller at the same time has no conflict occurring on console.