Well, those are the correct sound effects and any lack of volume is not obvious to me at the distance you took the video. If the volume had been turned down by the previous owner using a CAB remote, I don't think that setting would "stick" when using conventional transformer control but maybe someone more expert can weigh in if that is a possibility. However you mention in one of your posts having a remote and if it's a CAB2 then you can check whether the volume is all the way up using that.
The only other thing that occurs to me is that maybe your volume pot has developed a fault - which is not impossible given that the engine is now something like 9 or 10 years old. Or maybe it's a speaker defect but you'd only be able to do a visual inspection on that by taking the tender shell off.
