Mark levinson no 26 Rustling channel

Hello! The preamp Mark Levinson no 26 rustles one channel on a black background. what could be the problem? He recently underwent preventive maintenance with replacing old capacitors with new ones, but there is still rustling at all outputs and even in mono mode only one channel rustles. What advise to check? This rustling is not particularly annoying, but I really love this preamp and I want it to work like a Swiss watch 🙂.
Does it do it with the input shorted? If you have the schematic and an oscilliscope you can start at the input and look at one channel at a time, then go back and forth looking first at the good channel then the bad one as you walk your way through the circuit until you find at what stage the noise is being generated. Then look closely at the components at that stage. As mentioned above, look for cracked components, cold solder joints even reflow any joint that does look smooth and shiny. Worst case is you can swap one component at a time between the good and bad channel and listen between each move to see when the noise moves channels, not a great way to find the problem but it usually works.
Good luck.