if the mechanism isn't functioning properly with the coil specified in the manual, you need to fix the mechanism. trying to compensate for that using a stronger coil is a mistake for a number of reasons, and can do far more damage in the long run. i'd strongly suggest diagnosing the problem and properly repairing it.

Coils don't wear out. Just a long piece of insulated wire. Nothing to wear out. 50 turns doesn't sound like much, but for that coil, it's a pretty big jump. Google pinball coil resistance chart to see the difference between the two.

Problem likely isn't the coil. Make sure the wireform is aligned and tight. One loose screw can cause problems. Should be rock solid. If any screw holes are stripped, toothpick and glue them, then make new holes. If the plunger is original, get a new one. It there should be a grommet below the plunger and it's missing, get a new one. New coil sleeve too. Part numbers are in manual and all should be available.

Start with the simplest solution...

Fresh coil sleeves and check the 'cup' the ball sits in for excess play vs the plunger.

These VUKs use pass-through plungers so not a whole lot to go wrong mechanically except for sleeves, worn out tips/cups, and alignment.

What flynnibus said.... the cup in the vuk can lose its 'ears' (nubs?) and it will not shoot the ball properly up. Also, the wireform itself can get misaligned. It's a royal PITA to do anything with that area with the playfield in the machine as you have to access it from the top with the PF raised up. Remove from the game if you can.

If you can take a slomo of the vuk popping as well, it might be popping TOO hard and hitting the wireform and causing it to whack down instead of feed to the left.

This is an issue on the lower VUK as well, alignment is even more critical on that one but at least that one's easier to adjust due to location.

They do swell into the interior where the coil sleeve is though, which can bind movement and rob power.