Classic Phantom White not working reliably after upgrade

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I rolled back the firmware to 2.11.5 and that has fixed the issue. 

How to rollback the firmware: Turn off, wait for 7 seconds, Turn on, wait for 3 seconds - repeat the process 4 times.

Btw, when the device is turned on, do not wait for it come up make the woosh sound and then count 3 seconds. Just turn on switch, count 3sec and then turn it off.

I will contact Devialet support today to understand if there is any solution.

Steps I did:
1. Rolled back the firmware with above procedure. Tested everything yesterday night and things are working
2. Used the App to again update the firmware from f2.11.5 to 2.12.3 and then observed things are still bad. It is as if the device is muted. Even single pressing the back button does not make a noise. If I press the serial number of the device in the app, the device does not make a noise.
3. Again did the above procedure and rolled back the firmware back to 2.11.5. The old firmware is working satisfactorily.

I have never had upgrade problems before and this is the first time I am having issues with Upgrade.

** UPGRADE TO LATEST FIRMWARE AT YOUR OWN RISK ****