Your footage does not have enough discernable details in the places you are trying to repair and thus the algorithm can't generate a pattern. This isn't magic stuff, it's hard computer math and sometimes it simply cannot work. In your case the almost monochramtic lighting doesn't help, too. You may need to use other, more conventional methods like duplicating the source layer, masking and moving it in place or the clone stamp.
I don't see the footage, I just see a frame. It would be helpful to see the footage, but it would be more helpful if we saw a timeline with the modified properties of the layers showing and the settings for CAF. If I take your still, mask the dark spot, animate position to give movement, pre-compose, draw a mask around the dark spot, then set Alpha Expansion to 3, this:
Becomes this, which isn't bad.
If I set Alpha Expansion to 4, I get problems.
It makes me wonder about your workflow. Did you create any reference frames?