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...

I always thought it was just another form of coloration.
If tubes only added distortion or coloration, wouldn't all SS amps sound better? This theory is very flawed.... Buffers are also used for impedance matching, which can be very useful between the cdp and amp.
It's simply 100% inverting op-amp with tubes that eliminates distortions. It's beneficial for unstable components. Any IC or SS op-amp can do the same job except tubes bring its own pleasant previously mentioned coloration to the system.
As to tech problem ID the channel(make sure by swapping wires) and than replace the tube which don't have to be matched since dual triode being used is already matched to itself. Soldered in-place tube is weird. I used to have X-Can buffer where I could just unscrew chassis and change tubes.
... I also don't understand the benefit of tube being soldered in place. I always thought that tube socket
a)thermally insulating hot tube from the rest of circuit/PCB components; b)provides mechanical vibration isolation. On the long run the solder around tube pins looses flexibility and turns into the cold solder joint. I would definitely place tube socket securely soldered and than place the tube after cleaning tube pins. Maybe it's still good...
You can also verify by retouching the solder joints on each pin.