Firmware upgrade Omnitouch 4135 fails

[getmein]

We had the 4135 with firmware 1.5.12 and made an update to 1.5.25 with sd card. But in 1.5.25 it didn't connect again (previous it worked with OXO R10). After several attempts to put it back to firmware version 1.5.12 - without success - the device was brought back to the implemented Rev. 1.4.5 Oct 15 2010.

But it doesn't work with the Ethernet and does not get an IP with DHCP.
And it doesn't remeber its IP if we use static.

We try to make the upgrade to 1.5.12 again with sd card. The sd card is accepted - but it does'nt find a file and starts booting.

The file is named upgrade.kt in the root of the sd card.

Any ideas who do get it working again??