This should be the correct GRBL build: https://carbide3d.com/files/grbl11/grbl11e20161219.hex
For what it’s worth, we haven’t shipped a machine with GRBL 0.9 since around 2016. It’s pretty rare for us to upgrade machines that old these days, and honestly, our team doesn’t have much experience with the process anymore. Because of that, we’ve had to stop providing support for it.