I bought new nylon strings. I haven't had any problem with my old ones when I tune them, but my high e nylon string keeps snapping out of the pin. It doesn't break, it's fine, but it snaps out of the pin when I tune it and makes my pin fly away. It's hard for me to play now when I can't tune the high e string.
What pin could exist in a nylon string guitar? I am used to those on steel string acoustics. Usually for nylon strings on a classical guitar you need to literally tie them around the bridge. For the pin to work the string needs to have a metal bearing at the end. Even then these will sometimes be under enough tension to pop the peg or pin out. What I typically do is make sure that the end of the string is bent in a U or J shape. That ensure that the bearing hooks on the wood under the bridge and doesn't slip up. This has to be done by hand but is easy. Just use your thumb nail to bend the end of the string near the bearing twice at 90 degrees. Then insert the end into the bridge and apply the pin. You can pull the string with your hand and feel that it catches. If this is not the "pin" you are referring to or if your nylon strings do not have a bearing at the end then please clarify by adding to your question.