Diagnosing remote like this is fraught with peril because there's a few different things it could be and without being there... oh well ... the key comment to me is you said its the same thing one set did right at the beginning but then not after that. There's a technical reason I forget, something to do with the guts inside not being absolutely clean leaving residue that occasionally gets energized and moves around and that's the noise you're hearing.
If that's what it is, it can be anything from one and done to intermittent and only every once in a while to almost nonstop. I have one that's intermittent every once in a while- and never heard it even once while playing music. Only at idle. So for me its not enough to be worth the bother of replacing it.
However, after long experience with tubes it seems to me if a tube is silent for years and then starts developing this same noise, that's a sign the tube is on its way out. Yours are way too new for that. But something to keep in mind.
If that's what it is, it can be anything from one and done to intermittent and only every once in a while to almost nonstop. I have one that's intermittent every once in a while- and never heard it even once while playing music. Only at idle. So for me its not enough to be worth the bother of replacing it.
However, after long experience with tubes it seems to me if a tube is silent for years and then starts developing this same noise, that's a sign the tube is on its way out. Yours are way too new for that. But something to keep in mind.