I ran into a similar issue of not restarting after upgrade to _026.
It happened on a QMX and QMX+. They both stayed in USB drive mode showing both the _025 and _026 files. Could not turn either one of them on/off by pressing the Vol knob. I removed power cable and powered back on. Each of them came up on rev 26 and functioned normally.
To test, I back-rev'ed the QMX to _025 and re-installed _026 and this time it worked as normal. Dragged the file into the QMX USB drive and it copied over and it rebooted to rev 26 automatically.
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Randy, N4OPI
