The Wetransfer link has aged out. You can upload *.lbrn2 files to the forum here with drag-n-drop or the upload icon in the reply editor.
Do that for the two files producing “good” and “bad” results.
Go through the list of all the other things that can go wrong. Although everybody wants to believe the hardware is perfect, very often desktop diode lasers have loose screws. LightBurn layouts with different speeds and scanning patterns can trigger different mechanical problems, so it’s worthwhile to eliminate those.
For example:
Note that the loose screw got through the initial “checked all the mechanical parts and they seem fine” assessment. 
Although it’s written for Sculpfun lasers, you’ll recognize most of the parts and places where problems lurk:
https://diode-laser-wiki.com/documentation/guide-to-mechanical-adjustments
A thorough checkout can save many hours of back-and-forth.