If you are getting the spots at corners, you can try rounding the corners. The laser stops and then starts at corners without decreasing power.
If you are getting spots in the middle of lines, check the file for “extra” nodes. Inkscape likes to add a node where you union two objects. Even if the union should result in one long, straight line, Inkscape likes to place a node wherever the objects met. The glowforge may be pausing at the node resulting in a spot.
If it is neither of the above, well leather is notorious for being slightly different thicknesses from one spot to the next. You could be seeing burn marks in the “low” spots. Adjusting the power down or speed up could help, but could also result in the laser not cutting all the way through. I would also try using a masking on the leather if you are not already. The masking may absorb the pinpoint marks. And finally, if you are not seeing pinpoints or flashback on the backside of the leather, flip it over.