The ";" button for releasing the train brakes has no effect after the locomotive brakes have been used. I can recall this happening with the BR Class 66 as well and if I'm not mistaken another locomotive which I cannot recall (I think it was the DB BR 363). I am able to release the train brakes using the mouse to move the lever. A ticket has already been submitted but I wanted to share it here too to see if I'm the only one facing this issue, if there is a workaround or if I'm doing something wrong.
Oh! My bad, since I only copied the description of the ticket I submitted, I should also add that the last time I face this issue was with the BR Class 20.