Printer duplex possibility disappear after a few minutes

[Klaus Vink Slott]

Hi

I have a weird problem in KDE's printing dialog:

My printer is shared via a printserver using CUPS and Avahi and I have 
verified that Avahi announces the printer capabilities as Duplex True.

klaus at msien:~> avahi-browse -c _ipp._tcp --resolve | grep -i duplex
    txt = ["printer-type=0x901E" "Duplex=T" "Color=T" ...

Firefox and LibreOffice picks up this, and I can select Duplex Long or 
Short edge as expected. But trying to print from Konqueror or Okular any 
duplex option is grayed out and selection is stuck on Off.

However: If I open the Firefox printing dialog, select Long edge and 
press Cancel, then immediately enter the print dialog in Okular (or 
Konqueror), I can now select Long or Short edge print (and it the 
printer does duplex as requested)

I am runnning KDE Frameworks Version 5.105.0, Qt Version 5.15.9 (built 
against 5.15.9), cups-2.4.2 on OpenSUSE Tumbleweed.

Where do you think this bug should be filed? OpenSUSE, KDE, or maybee CUPS.

-- 
Regards
Klaus