Mageia 5 beta 3 no longer boots

[bertaerts]

I have a Dell Inspiron 17R SE 7720 which is capable of UEFI and legacy BIOS.

My internal SSD contains Windows 7 and Mageia 4 in BIOS mode.
As soon as Mageia 5 is released, plan is to install Windows 8.1 and Mageia 5 in UEFI mode.

To have a working system while re-installing the internal SSD, I have Mageia 5 beta 3 with all updates on an external USB disk.
Partition table is GPT and install/use happened/happens in UEFI mode.

Yesterday I've put my PC back to BIOS and booted Windows 7, WHILE external USB disk was still plugget in.
Windows 7 succeeded in damaging/removing the GPT partition table, just by booting Windows 7
Once back in Mageia 4 with GParted, external USB disk seemed empty, no partitions.

Fortunately I found the tool testdisk in Mageia 4 by Googling.
With testdisk I could restore the GPT table and could access my data again.

But unfortunately I can not boot from my external USB disk.
Grub2 is not found.

How can I restore the booting of Mageia 5 beta 3 on the external USB disk?

https://wiki.mageia.org/en/EFI:_can_no_longer_boot_into_Mageia
I tried the option with the rescue function of the non-Live 64bit Mageia dvd.
But it gave an error, don't remember the exact words...

[doktor5000]

Can you please list the contents of that disk in terms of partitions?

[bertaerts]

The GPT partitions on my external USB disk are:

/dev/sdd1 fat32 MGALIVE /boot/efi 100 MB
/dev/sdd2 ext4 root / 97.66 GB
/dev/sdd3 linux-swap 8 GB
/dev/sdd4 ext4 home /home 390.62 GB
/dev/sdd5 ext4 backup 244.14 GB
/dev/sdd6 ntfs ntfs 190.96 GB

[bertaerts]

When booting with Super Grub 2 disk, I can boot into Mageia 5 beta 3.
But only in command promt.
startx mentions issues with nVIDIA.
And during boot several times "failed to activate swap partition" is mentioned.

[united4]

My guess is that this might be a hardware problem, especially if your USB device is a solid state one. Maybe it has turned into read only mode, and in that case you are lucky you can restore your data but don't think you can do much more.

[bertaerts]

I could recover my data on my external HDD USB disk (not an SSD).
But I was not able to make Mageia 5 beta 3 boot again
I already re-installed M5B3 keeping my /home partition.
Now I am installing all my applications again...
For sure there is no hardware problem with my USB disk.

Does anybody have an idea on why Windows 7 has destroyed the GPT partition table on my external USB disk?
I will never leave this disk connected when booting Windows !!!