One dish to 2 recievers

you can sometimes get signals the same on other sats thats why you see signal but no pic on fta channels i would say get a triax 1.1 dish and multi lnb arm for the front of it and follow the instruction booklet for the arm it shows you the distances apart for the lnbs , doing this pick up 28e first and you will find the rest with sloping the bar and moving them allong the bar a little til you get the sweetspot for signal , i filed the inside of the lnb holders so they moved along the bar more freely and it made life a hell of a lot easier , in the end i got a motor to increase my options it also worked out that it would have been the same price when you count the cost of the arm and 4 twin lnbs and diseqc switch as opposed to a motor and 1 twin lnb you will need an 18inch t&k bracker for a triax 1.1 to get a good turning arc on the motor or you will be too close to the wall if you go this route but you need a t&k anyhow , hope this helps you

Have you done a scan of 23.5 or added a up to date channel list? You may have old pid details entered or have similar freq details so the stb shows signal but won't be able to view.

you will only pick up signal from 23.5 if you dish or lnb would be aligned to that sat if your aimed at 28.2 east you can't pick up 23.5 some transponder might have the same value this might make you spiderbox think it has signal on 23.5e but really it hasn't.
I have a fixed triax 1.1m dish with a multi bracket with four quad lnb's and several boxes around the house wich pick up 13e+19e+23.5+28.2