You are totally right there is a bug when switching from MIS 8PSK to QPSK.
The problem was to find a FTA QPSK to test.
So here is how I reproduce your problem.
I scan on Hotbird 13.0E
DVB-S 12597 V 27500 3/4 QPSK
There I choose the channel: RT Doc
I have sound and image, then I zap to:
Atlantic Bird 3:
DVB-S2 11508 H 29500 8/9 8PSK Gold 50416
Channel: M6
I press 0 to return to RT Doc
No sound no audio
And after a while we have: No data on transponder! (Delay expired when reading PAT)
But the funny part is that if I press twice blue to enable PiP, in the PiP window RT Doc is playing fine (of course no sound).
So main screen RT Doc is not working but the same channel in PiP is working.
And as you mentioned zapping to any standard 8PSK channel then back to RT Doc I have the image and sound.
Edited by Pr2, 26 May 2020 - 23:04.
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Sat: Hotbird 13.0E, Astra 19.2E, Eutelsat5A 5.0W
VU+ Solo 4K: 2*DVB-S2 + 2*DVB-C/T/T2 (used in DVB-C) & Duo 4K: 2*DVB-S2X + DVB-C (FBC)
AB-Com: PULSe 4K 1*DVB-S2X (+ DVB-C/T/T2)
Edision OS Mio 4K: 1*DVB-S2X + 1*DVB-C/T/T2