If Ted's suggestions don't work, here's what I do (I had a lot this season and am down to one). I have a Channel-Lock pliers with rubber-covered handles given over to going in my pool water. I use it to un-plug the screw-in plugs in my drains and returns.

The back of the tool is round and won't cut the liner. I work from the point where it's half in / half out of the track and put the rounded head of the pliers under the bead and push up with a rolling action to move the bead back into its track--one angstrom at a time! I try to do it on a sunny afternoon when the liner's been baking and softened--not to fond of a hair-dryer near water, especially when I'm in the water! I work it from both sides until finally it pops completely in to the track.

Carl