Print bed won't raise high enough

I've just replaced my hot end. When I went to level the bed manually, I notice the nozzle was almost 1cm away from the bed. So I tried adjusting the offset, but it seems to hit a point where it won't raise any further. The z motor seems to knock and 'skip' but won't raise higher. The z-offset value keeps decreasing even though it's not actually raising. The video shows the issue.

I've tried turning it off and manually raising the bed, but it stops at the same point, so I'm not quite sure what to do here as I'm still a noob at this stuff.

Using a Flying Bear Ghost 6.

Any ideas?