Musical Fidelity Buffer

I just purchased a used Musical Fidelity Buffer for an old solid state system just to experiment with. I hear a small crackling in the right channel, and wonder if anyone has had that problem. If so, does it go away after a few hours of warmup, or should I just send the thing back and forget about it.... This is the X10 V3 model using the Trivista tubes which are soldered in place.
One of the tubes is probably going. I have matched replacements at 50.00 for a pair.

I have been using one for years that runs at least 15 hours a day without issues. I choose to perform cap upgrades and matched tubes, which was a big difference when I first purchased it, several years ago.
I never could understand why anyone would insert a device in the signal path whose sole job is to introduce distortion into the system. And let's face it, that is *exactly* what a tube buffer does, plain and simple.

I thought the whole idea was to keep the signal path as short as possible with as few components as possible and still get the job done...