There seems to be issue that keeps cropping up in your preserved collection. The sounds are lapping over each other. Am driving the class 33. It sounds like a thuding noise from the engine. Its becoming unplayable to drive. I've noticed this with the class 377 as it crops up aswell. You can hear it more viewing out the cab. Restarting acts as a temporary solution. But the issue is there.
Whenever this happens to me, I go on the free cam and go as from away (so the train is inaudible) and jump back into the cab, this has always fixed it and it rarely happens for the service again.