It seems there is no simple solution to your dilemma. If I understand your configuration correctly, you have a single motorized dish with the main being a twin lnb with one output connected to the motor, then to your tuner A. The second output and a second and third lnb connected through a switch to tuner B? After you tune to something on 23, the dish has moved, but when you then try to tune to something on 28, the "logic" of enigma is that tuner A is on 23 and 28 is available on tuner B, so it tries to use tuner B, which of course does not work because it is now also pointed at 23.
If you make tuner A preferred, then if you try to tune something from sats 19 or 13, it will use tuner A and move the dish, which will limit you to that one sat. (All lnbs for tuner B will be pointed at wrong sats relative to your config.)
If you make tuner B preferred, then when you tune something from 28, it will use tuner B, which will basically create the same situation you currently have.
A few possible workarounds:
Change setup so tuner A is "positioner, selecting satellites" then select all sats you watch except 19 and 13 (do not delete!) Then set preferred tuner to tuner A. Only downside is you won't be able to watch/record two things on 19 and or 13 at the same time - maybe not a big deal for you??
If you do not record often from 19 or 13, you can try setting the preferred tuner to auto and set preferred recording tuner to tuner A. Then if the sat is "stuck" at 23, if you try to record something to on 28, it "should" try to use tuner A and move the dish back to 28. Downside is if you record from 19 or 13 it will move the dish, making 28 unusable until the recording finishes. One workaround for this is to always start a recording on 28 just before recording something on 19 or 13 - this will lock the dish on 28 and force the recordings for 19 and 13 to use tuner B. After the recording on 19/13 starts, the recording on 28 can be stopped, freeing up the dish.
If you leave your setup as is, when "stuck" on 23, choose a channel on 28 and start an instant recording, then immediately choose another channel on 28. This "should" lock tuner B for recording on 28 and force the second 28 channel to use tuner A, causing the dish to move back to 28.
There may be a way to use the advanced setup on tuner B, but I can't think of one off the top of my head....
