Trayson, I have broken 4 of the plastic "levers" from harbor freight as well. I assumed it was from it trying to compress the water that gets between the plastic frame and the rubber cup so I drilled a small (1/8" iirc) relief hole in the plastic on each side. Since then I have only broken one lever, but I think the key is to work the lever back and forth instead of one forceful motion to lock it down.

I ordered that yellow cup last week and threw it in the boat so if another breaks I can switch to those.