That's very strange Nikolaos!
Which BSP do you've installed on your devices?
one thing that you can try is to upgrade them using the adb option in the recovery menu, and then follow the instruction on the device to send the recovery package using the
command from your PC.
My units are on 1404 non-GMS build. It looks like the images posted on our support site are not signed. I even tried to install the one which is on the device (1404 non-GMS), same error.
I am leaving the adb option as a last resort, I have asked the partner to open a case as well. It's strange because a few weeks ago we did the same with 2 other units and all went well.
which Osbuild in on the unit goto Settings / About Phone / build number
which Exact zipfile are you trying to install.
OS build on the unit is 01-23257-K-14-04-00-MV
The file I am trying to install is the 1404 build (GMS) on the support site at
copy the file to an external sd along with the reset files and follow the process as in the release notes. Factory Reset works, image update fails on the signature and aborted.
can you do a Factory reset and then reboot and go again into recovery mode and apply T75N0KEXAPUEF01404.zip 573 Mb
if it still fails make a screen shot / photo of the exact failure message
reboot the terminal and goto MLog and Export all Logs
and sent all to me.
this is what finally worked as it seems.
Placing the files in external SD card and try the upgrade yields a signature verification failure and aborts. Only factory/enterprise reset works this way, not the image update.
Trying to copy the files to internal storage from the external sd, stops at around 128GB (hangs) using the integrated file manager of the TC75
What finally worked was:
Boot to Recovery
Copy files to internal sd from the PC
Reboot to recovery again
Install zip file
I guess the external SD method has some glitches or does not work as expected, at least in our case. Anyway, that's an urgent case that does not leave time for further testing as the terminals need to be delivered asap but let us keep it in mind in case we run into something similar in the future.
Thanks to all for your input.
what is type / size and manufacturer of the sd card in use ?
Kingston, micro SD, 2GB. Same card has been used in several upgrades in the past with no issues. Anyway, let's see if we can reproduce the problem so that we are ready in case of similar issues.