Flashtool stuck at modem.sin

Hi,

Before unlocking the bootloader on my Xperia Z5 Compact, I want to backup the drm-keys. This can only be done be rooting the device, without unlocking the bootloader. To do this I need any version prior to 32.0.A.6.200. So far so good.

I've used Xperifirm to download an old firmware version (several, actually) and tried to flash it using Flashtool. Here's the problem. It never gets past the following lines:

Code:

---

20/038/2016 11:38:49 - INFO  - Processing modem.sin
20/038/2016 11:38:49 - INFO  -    Checking header
20/038/2016 11:38:49 - INFO  -    Flashing data

---

Yesterday, I've waited for several hours for it to finish, but it never does.

What I've tried so far:
- different cable
- different USB-port
- different computer
- several firmwares from Xperifirm: they all fail in exactly the same way
- Restoring the firmware with the Xperia PC Companion: works like a charm, but I'm stuck again with the newest firmware again

Also: I've created an .ftf file from the stuff the PC Companion downloads and when using that in Flashtool, it doesn't work either. Using the official PC Companion however does work.

My Z5 Compact (E5823) is non-branded and should be without simlock.

Thanks a lot!

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