I'm running Mach3 at home. w a 2' x 3' table. a 60 90 from china nice place in Chicago. I would have to look at the board/mfg to tell you more.
I'm a professional prototyper in the bay area. At work i use Haas mills and Surfcam, but at home i'm doing topo maps and stuff and my pro software doesn't handle STL files well and doesn't do nice heightmapping like your system. easiest 180.00 i ever spent.
I hadn't had the time to pick out what might have caused the issue. in mach3 display the toolpath just went off positive in x for ever.
i'll add in that g40
in 25 years anytime i've needed to modify a post, i had to relearn it. as I've needed to do that about once every 3 years.
oh.. and took some digging but I found a nice gray scale mapper that is much easier to use then the USGS
might want to pin it.
https://tangrams.github.io/heightmapper/#11.375/39.0487/-122.8176