GRBL sends ERROR:33 when CHECKING generated GCode.

I am running Fusion 360, UGS, GRBL(on an original Arduino UNO R3). I have POSTed many tool paths since building my machine and have never encountered this error.
Fusion generated a 97000 line tool path. When I run UGS in check mode I get the error seen in the attached picture.

Attachment 429156

Have any of you encountered this and fixed it?
Attached is the Fusion file if you care to look at how it is set up.
The tool path giving me the error is called 2D pocket1 (2). All the others run fine.

Thanks

That error is generated when Grbl can't figure out what the internal representation of the arc should be from the co-ordinates specified. Usually this is the result of specifying a center point that isn't actually in the center of the arc.

As to why Fusion is generating something that Grbl doesn't like - I don't know; and I'm sitting in a restaurant right now so I can't try to debug it. One of these days I probably ought to put together a portable Grbl rig that I can just throw into my laptop bag, but for now all my machine tools are at home...

Anybody else??
Please

So, it's something in the G-Code. I'd try to figure out the offending line, track it back to the specific tool path and then the specific feature in your model.

By the way, if you have a spare arduino, you can hook it up, load grbl and debug from your dev machine so you don't have to run it on your mill/router.

UUGH This error is all over the carbide motion and x-carve boards with lots of different "resolutions". Was hoping to get more info here. I really don't know g-code but the error line is posted in the initial post.

I downloaded the latest post from the autodesk posts library and reposted this tool path but I have the same issue. I am a noob with g-code and dont think I have the skills to figure this out.
Any help would be DEEPLY appreciated.
Thanks