I figured out the issue, and wanted to put it in here for other people who might run into this.
It turns out that there is a known issue with the G90 that it stop transmitting every now and then, and you have to give it a whack by the antenna connector (like, physically mack it), and it will start working again.
I reluctantly tried it, and it started working for about an hour. another whack got it working for another hour.
I am gonna put it on the bench this weekend and see if I can suss out what is going on. I think It's been too long for this to be covered by warranty, but I'll check.
Thanks for all your suggestions, everyone!
