Streaks on engrave

Hi. So far so good.I have made wood cuts, wood engraves, cardboard engraves, textile engraves, jar lid engraves… but this last textile engrave has me puzzled.

There are streaks on the lettering. Long long streaks. Might be a software bug? The setting was 200mm/s, 15% of 10W laser.
LaserTekstilSH.lbrn2 (115.1 KB)

Lightburn is 1.3.01