I just tried updating a Xenon in a Ethernet featherwing Mesh gateway to 1.5.0-rc.1 to take advantage of the bug fixes with the SPI bus mutex. It appeared to go fine - but after flashing it did not publish anything but the cloud events “spark/status” etc. I was using the Workbench to compile and flash.
I rebuilt using 1.4.4 and after another successful flash it restarted but wasn’t publishing. After doing a pin reset it restarted OK and began to publish correctly. I didn’t see the Xenon do any kind of update. Then I recompile with 1.5.0-rc.1 and this time it restarted correctly after flashing.