I know what's wrong... The phone skips like that when someone is USSD attacking your phone, they do this to steal your information and data, and music, you need to install an app to protect your phones from being hacked. I hate McAfee but they brought out an app to stop people hacking your phone this way, the only solution I have found that has stopped my music from skipping, and my voice dialer having a mind of it's own ruining my listening experience with my headphones, this happens with or without headphones, USSD is an vulnerablity of Androids that allow people to hack you and your stuff and steal your stuff.
If you really want to get rid of this back up your phone, factory reset, then from a fresh install install mcafee dialer protection.