Default [Q] P6810 - not possible to install correct 4.4 rom

I tried to install the KitKat Rom on my P6810 Tablet. It's not the first time for flashing it but now I had a very strange problem. I tried 2 different roms, one was the OmniROM, and both had the same problem:
When trying to flash the 4.4 Rom for P6810 the CWM says that the rom is not for my tablet. Something like not the right type. Then I found out that I can flash the i815 - Rom. But when starting my tablet after flashing the i815 - Rom the touchscreen is not working. I'm sure the reason is that the i815 Rom does not have the correct display driver for my P6810 Tablet...
But why I can install an i815 Rom (which is not the correct one) but no P6810 Rom (which must be the correct one)? Is there anyone with the same problem?
Thank you very much in advance