Fill is wobbly while Line looks good?

It looks like your laser is losing position as it makes scanning movements, but not Line movements. Check to make sure your belts are tight - particularly in the dimension your laser is losing position in (that is probably ‘X’, or the left-to-right dimension).

If that doesn’t help, try reducing the speed at which you’re running your Fills at. Sometimes a particular combination of speed and acceleration can reduce mechanical resonance, leading to the effect you’re seeing.