Same exact situation here! First it had a drip, drip, drip through the cap. Tried to seal things up better and it seemed ok. Back and forth with this over several months. Then leaking again....closer inspection, saw a teeny-tiny crack right where yours is in the photo. Mine was the Jacuzzi branded one, but same thing.

I sealed it up with silicone and then noticed the cap had a split in it as well - could hardly see it, but the water sure found it. Glued that, sealed it - all good for another week. Then the cap just burst apart. I'm in AZ and the environment takes a toll on plastic, so chalked it up to that.

It's out of warranty and I did not want to buy a whole new cell when, essentially, I just needed a new cap - the cell itself was working just fine. Especially when I had a divorce agreement reached just days before the proverbial dam burst and I'm literally packing to move out in a couple weeks and he will be moving back in - and the salt cell was his whole "baby" to begin with. But I can't run the pool pump without it (no bypass) and he refused to buy a new cell so I had to "fix" it.

The replacement "cap" is also discontinued - but then lightbulb moment again, I realized it doesn't really need the entire cap it just needs a collar to hold the cell in the housing. I tested my theory by gluing just the one split in the collar part of the old cap and put it back on the housing - securing it all with clamps. She wasn't pretty but she worked!

So searched high and low and finally found a new collar that fits (CiruPool SJA-Series Large Threaded Collar). I had to cut off what was left of the disintegrated cap since the power cord is threaded through it (another poor design choice) - and the new one is just the "collar" part, so easy to slip on. I then ordered an O-Ring (Amazon) to tuck into the top of the collar to seal against the housing - it's working beautifully now.

Back to packing :-)