LightBurn makes no changes to GRBL’s settings at all. I can’t say whether PicSender does or doesn’t, but it might set a workspace offset, which would cause problems in LightBurn.
This might help: Origin set, but can't delete it
Try running the $# command referenced in the above post and see if PicSender is offsetting your machine origin. That’s the only thing I could think of that would produce the result you’re seeing, and it wouldn’t be uncommon for CNC software to do that.