[TJ Mason]

It might be that it was re-served with a different number of twists to when it was originally served. People have very different ideas about how twisted the string should be when serving -- my preference is for slightly fewer twists than when shooting, but some use loads of twists or hardly any.

Or maybe someone tried doing the centre serving on a string jig rather than on the bow. The string would be less tense, resulting in the string material being kinda stuffed into the centre serving rather than wrapped properly.

Either way, the best option is learning to do the serving yourself.