It's probably a blown worm gear. Abu reels (those made in Korea or China) are famous for this.
My thoughts exactly.
What I would do is get a new worm gear, and while you are at it, get also a new pawl.
Then, put your Kalex in the drawer as a back up, and get yourself a C3 or C4 made in Sweden, or even better, a Record.
Or, ask KenD on the forum if he would customize a nice lefty Ambassadeur for you.
It will save you money in the long run.
Those BCX and Kalex reels are disposable crap. A waste of reel money for anyone but the occasional angler, IMO.