I've just come back to this thread and got really riled up about it.
It riles me up a lot that an annoying background buzz on an RS6 engine is accounted "normal." Please note that the noise factor is not consistent across all such engines; my VL GE Evo does not have it; my VL Genset and ATSF 3000 do whereas in other people's videos of the same engines there's no such noise.
But what riles me up even more is, in a word, Fastrak. I have not got a good word to say about it except that the command control switches are fun when they work; everything else about this track is highly problematic. You don't need a multimeter to check whether the connecting spades/prongs at the end of each section are loose, cracked or missing; Fastrak is prone to all of those things and when they occur engines can start misbehaving. If the OP disassembled, moved and reassembled his layout, with Fastrak any of these things could be causing a signal/track power issue. The symptoms the engines are showing all seem consistent with that.
(P.S. I see that there is now a thread on Fastrak breakages here: https://ogrforum.ogaugerr.com/topic/fastrack-9. This confirms what I thought was the case i.e. that there was a batch of this track with bad pot metal used for the connecting prongs so they are prone to snap off.)
I've already posted above that my ATSF 3000 had both a RUN/PGM switch problem and a more serious board failure. I can't exclude much the same thing in the case of the OP's engine. But to have a change in performance of two other previously reliable VL engines after reconstructing a Fastrak layout strikes me as very likely to be a track and/or power supply problem rather than anything else.
