Fixing liner pull-out from channel?

My liner is about 5 years old and doing well except for a few areas where it is pulling away from the channel along the top and I can't manually pop it back in. Does the pool have to be completely drained to fix this? And if I go to that trouble, what are the chances it won't pull out again when re-filled? I'm afraid if I do nothing then it will really start pulling away next season.

You can try the advice here

If that doesn't work, let me know;)

Thanks for all the info. My liner is just pulled out about 4inches wide but not far from the track, so one of your methods should work.