That is a minor problem...somehow ya need to oil the 2 springs that engage that..

The magor problem is taking it apart..I believe you can oil that mechanism without disassembling the reel..when you push the button note the little hole or slot..to the right of your reel...shoot some reel oil or gun oil in there..and then work the reel so the oil is spread out good..
I've had a few reels do that..

I had one rod my son reeled in from off the bottom of the lake..I took it all apart and put it back to gether,,worked great..THEN..I've had some and was over confident..and messed the reel up..SO if ya ever do take one apart...memorize where EVERY part goes..becasue down to the smallest flat washer makes a huge difference.

Most reels have 2 main screws in which the entire right side comes off...then you can see all the little springs and shoot some reel oil..DON'T use any oil heavier than reel oil..another lesson learned.I've taken many apart..some success stories and some not.