Xperia Z3 unable to charge - able to connect in flash mode - backup possible? wipe?

[paysen]

The problem:

My Z3 isn't charging at all, it's showing the charging screen and the red led is glowing for a few seconds, then it's turning off, showing the charging screen and the red led for a few seconds, turning off and repeats that without actually charging the phone. I can't turn it on, but I am able to get into flashmode by holding down the volume button and connecting it to my pc.

I already flashed the stock image. It's rooted and was running the latest official image. Locked Bootloader.

A few days ago it started changing the battery status every few minutes. Going from 12 to 50%, staying on it for a few minutes, going back to 20, to 6, just random numbers.
I used it today when it suddenly powered off. Despite being charged for one and a half hour in my car with the dock connector. Since then I am not able to turn it on or charge it.

What I already did:
Testing multiple chargers and cables, incl dock connector.

Tried to backup it with adb console, however it can't connect to my device. But I have zero experience with ADB, so I tried the flash tool from androxyde. It's connecting in flashmode and I was able to flash a stock image.

Am I able to backup the phone from the flashmode?

If not, am I able to wipe it so the service isn't able to view my personal data?

I hope somebody can help me :crying:

 

[paysen]

I was able to charge the phone now, I used both, the dock connector AND the USB connector cable. I don't know if it's damaging the battery but it seems to be broken anyway. Still giving out random numbers (was normal until it went past 10%, now it's jumping between 50% and the real number.

Sad thing is, I wiped all the data on the phone. Good thing is, if it wouldn't have turned on, nobody would be able to see my personal data.

It's time to give it to a service point I guess. I hope I get a new phone btw, seemed to have a faulty antenna as well the last weeks.