The worst sort of fault.

All I ever do is double check every cable I use, especially to see if there is any movement at all in between the parts of jack plugs. Movement of any kind in any direction is a no-no and the jack must be replaced.

A large proportion of all the signal faults I have ever had could be traced to a dodgy jack plug. I estimate I get 5 times as many jack failures compared to internal cable problems, and 5 times as many cable failures compared to XLR connector faults.

I now find the "moulded-on" jack-to-jack cables cheaper to buy than building a jack-to-jack cable from parts, and reliability is at least as good.

It's just unfortunate that XLR's are not fitted to keyboards until you get to "professional" priced units. If the jack outputs on my PSR 3k go dodgy I may well do some case butchery and fit an XLR output stage. However, credit where it's due, never had a problem with the output jacks on any of my three PSR's (630, 2k, 3k). I reserve judgement on the noisy volume controls, however (the 3k is OK so far)!