It could be for a few reasons, your most likely not leaving enough slack when putting on new strings, if you cut the string too short that will most likely keep happening.

The best way to prevent this would be to measure the length of the string about a post and a half up from whichever tuning machine post your planning on putting the string through.

Next, make a bend in the string a that measurement and use it as a marker when feeding the string through the post.

You’ll want to stop feeding the string through when you get to the bend. Absolutely make sure that you then tune the string before cutting off any excess wire.

Do this to all your strings, then tune up the whole guitar a couple of times. Now your good to clip…if that was the problem causing it you should definitely see some improvement right away!