[luka]

Are you using any spacers between the flattener and the t-ring adapter?
edit: I meant before you used filter when everything was working.

In my case I had to put the filters before the flattener. The flattener required the distance to the sensor to be exactly the thickness of the t-ring + DSLR distance between the flange and sensor. In other words it is not possible to insert anything else between the flattener and the DSLR.