I'm not sure if this is normal for unicable LNB's but I set my preferred tuner to C and my preferred tuner for recordings to D.
I was expecting this to leave the main tuners A & B free to avoid a black screen when scanning with ABM but I just get the 'cannot get the NIM' message.
If I reset the preferred tuners to Auto then it works fine.
Tuner A is 28.2E and Tuner B is 19.2E.

Not really an issue but I was expecting a different result.