Believe it or not the 1/4 inch adapters are of various specifications. Meaning that you should buy a few...as chances are with other 1/4 inch to 3.5mm (I’m assuming that’s your adapter) will often sit better to connect the signals. I have had this happen on rare occasions also. Just try different adaptors, no need to replace whole cable. The interesting part is with you it’s either all on or off maybe to one side? The really serious situation is when it’s almost not noticeable, but a slight sound degradation is occurring! That’s almost hard to spot!

Thank you.