Bootloop / Frozen on Unlockedd bootloader

Hello!

My RazrI got into a bootloop (red boot animation) without any reason (the phone worked since over a year without any tweaking around with stock firmware). I got it into fastboot and tried to flash CFC_9.8.2I-50_SMI-26_S7_USASMIJBRTEU.xml with RSD but at command 4 (reboot bootloader) it failed. I also tried the MEDFIELD unbrick fix, but this didn't help also. So I executed each fastboot command from the RSD xml manually. I flashed gpt, motoboot, boot, recovery and motobp with success. But I got an error on system:

Invalid sparse file format at header magi
error: write_sparse_skip_chunk: don't care size 701911720 is not a multiple of the block size 4096

a few other lines with this block size problem then:

sending sparse 'system' (99096 KB)...
error: write_sparse_skip_chunk: don't care size 701911720 is not a multiple of the block size 4096
error: write_sparse_skip_chunk: don't care size 701911720 is not a multiple of the block size 4096
OKAY [ 9.108s]
Writing 'system'...
(bootloader) BLKDISCARD ioctl /dev/block/mmcblk0 fail
(bootloader) Fail to erase partition
FAILED (remote failure)

The same result with flashing cdrom.
Then I tried to erase the system with fastboot erase system and got the following error:

erasing 'system'...
FAILED (remote: Permission denied)

I also tried to erase the cache with the following result:

erasing 'cache'...
(bootloader) BLKDISCARD ioctl /dev/block/mmcblk0 fail
(bootloader) Erase cache fail
FAILED (remote failure)

My bootloader is unlocked. After getting the first time into fastboot, now the phone hangs on the "unlocked bootloader" screen for some time and the resets und loops this way.
Is there any hope to get it working again?

Thanks!