Music Issues in iPhone 5S

Hey guys, ill start by saying that maybe this is my own fault but it has been bothering me for the longest time.

So ill be the first and not the last to say i probably have too much music on my phone (4000 songs) but im still wondering about this issue.

After times that i sync my phone with itunes i find that multiple songs every once in a while either dont play and skip right away or skip part way through the song. I dont use my phone or anything while it syncs either. These are sometimes also the same songs that have worked perfectly fine multiple times before a particular sync.

I can say as well that every song i have plays perfectly in itunes on the computer. This is just an issue that has been racking my brain for a while, hopefully someone might know whats happening.