After lengthy debugging, the Rainbow now boots DOS 3.10 (with a proper NVRAM file that must match DIP / RAM Settings)...Still, DOS 2.01, DOS 2.05, DOS 2.11, CP/M 2.x _and_ Concurrent CP/M fail with quite the same error!
Now i have a good log from an attempt to boot Concurrent CP/M - together with a commented source file from Digital Research (-> right hand side -> WD1797).
It shows why the seek to track 00 happens - instead of a seek (or read) @ track 2 - as expected.https://dl.dropboxusercontent.com/u/37819653/SEEK_TO_TRACK_0_in_case_of_error.jpgpattern T0 -> T1 -> T0 repeats with all 2.x disks mentioned.
As always, some hints would be nice. I am a bit out of ideas...