Problem when filling a figure (undulations)

I’d guess some sort of modulation of the laser power. The top two look like the same pattern , so I’d be interested to know if it was power or speed that changed between them. I’d also be interested to know if the material was moved between burns, because that could help prove or disprove Colin’s flat spot suggestion. (They’re slightly offset in x - a flat spot would have stayed x aligned).

If the laser power isn’t steady I’d guess the culprit is the PSU, but it could also be the emitter.