@Labox: I don't have the payware registered version of FSUIPC and so my Saitek X52 is not extra calibrated. (But as you can see, throttles are working)
@Giora: Lek767 already replied while I'm writing
@All/Lek767:
I use the recommend start procedure from Angle of Attack 737 Training and just crosschecked the FCOM procedure, so its Packs Off ->all bleedair valves open and crossbleed auto or open ->Starter GRND->Waiting for increase of N2 >=25%->Engine start leaver IDLE->Watching EGT/N2 increase until starter cuts out.->Next engine ->Both engines stabilized->Generators on, APU Bleed of, Packs Auto->Apu off
Most of the times, (and in this case I took the screenshots from) I use the default NGX Cold&Dark Panelsetting set as default startup panel state, and then load PAX and Fuel via the FMC. (If Bug happends, no active failures are displayed in FMC PMDG Options)
I choose a 737 on the free flight fsx panel, but I don't set one up as default flight (as recommended by PMDG due double loading issues) and don't switch from one loaded 737 to another.
I only used cntrl+E after the bug occured, and this keystroke or the activation of the reversers (as seen in the screenshots) seem to help. Just wait or reload the panel won't work (as read in my initial post)
Image EICAS before a normal start:
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