I had a Zero4K equipped by 4.4 easily configured to act as client in fallback configuration from the Ultimo 4K (equipped by 5.1.008).
Now I tried to use also a Solo4K's tuners connected to the Ultimo4K in fallback mode. The Solo4K has got in flash a clean install of 5.1.008.
Well: trying the usual client fallback configuration, a the GUI restart, the box shows a tenth of time the spinner and the stops showing also the spinner and gets stack at the "Starting GUI" screen and nothing is possible but switching it off. Also the complete reboot doesn't act differently. I also left the box on for many minutes but nothing.
So, as I have OBH 5.0 and OBH 4.4 in OMB, I tried to use the fallback client configuration by 5.0 and it happened exactly the same thing at the GUI restart.
Instead, by 4.4, by chance the same version on the Zero4K that has always perfectly worked, was immediately and easy to have the fallback.
So, there seems to be a problem in the combination 5.1-->5.1 or 5.0-->5.1 but not 4.4--->5.1.
Now I tried to use also a Solo4K's tuners connected to the Ultimo4K in fallback mode. The Solo4K has got in flash a clean install of 5.1.008.
Well: trying the usual client fallback configuration, a the GUI restart, the box shows a tenth of time the spinner and the stops showing also the spinner and gets stack at the "Starting GUI" screen and nothing is possible but switching it off. Also the complete reboot doesn't act differently. I also left the box on for many minutes but nothing.
So, as I have OBH 5.0 and OBH 4.4 in OMB, I tried to use the fallback client configuration by 5.0 and it happened exactly the same thing at the GUI restart.
Instead, by 4.4, by chance the same version on the Zero4K that has always perfectly worked, was immediately and easy to have the fallback.
So, there seems to be a problem in the combination 5.1-->5.1 or 5.0-->5.1 but not 4.4--->5.1.