SKIPPING CD ?????

Afternoon......new to this forum so please ignore my ignorance.

I've got a cd multi changer in the boot of my S4... i think the head unit says "concert on it". when i play CD's every now and then it's skips or completely cuts out with "ERR" on the display.

i have tried cleaning the lens but still no joy.

It also seems to happen more frequent at high volume....or maybe that my imagination.

Any ideas ???

i understood what you meant......checked this and it's set correctly.

I have tried loads of different Cd's but still no joy.

Any other suggestions ???