As 81BB said, could be as simple as needing to blast the dust out and lube up, only need to grab a little and enough that they may not self-adjust and cable has reached its limit. Or even another post had where they had the wrong adjuster sprockets each side and essentially undoing adjustment each time it was reversed. The sides are colour coded in gold or silver plating, only good when not rusty. This is the same reason many drumstudents didn't even have an adjuster cutout in the back, wasn't needed.