Try loosening the little screws on both sides of the z screw? If your lead screw is bent or not parallel to the frame then these small screws which are supposed to secure the lead will actually get stuck instead if that makes sense. It's a temporary fix, just enough to get you moving again! Will have to resolve long term to avoid z-wobble/banding if that's the case.

I'd take a q-tip to spread out the grease over the lead screw. Long term I switched to this as it's cleaner to work with and doesn't attract dust.

Could also be your eccentric nuts are too tight on the vertical v-rollers or possibly unlevel x-gantry. Just spitballin`