That line puzzled me so I tried, and… I reproduced the issue on my machine.
I suspect it has to do with the fact that the leading “/” in the MDI command indicates that CM should pass the commands straight through to GRBL with processing them, so CM does not see the G90 (absolute mode) command, and probably think it’s still in G91 (relative mode), but GRBL is now (still) in absolute mode.
Somehow this throws off where CM things it is for jogging, and when you tell it to go 1mm to the left, it takes what it apparently now thinks are the current coordinates X=-5,4750 and Y=-10.1, substracts 1mm to X, and generates that jog command towards X-6.4750
And sure enough, I retried but this time I sent “/G91” after “/G90G0X-106.125Y-298.850”, and then jogging 1mm to the left works as expected.
Moral of the story: if you cheat on CM by talking to GRBL behind its back, be sure to clean-up and leave things as you found them, before it comes back