I have a gen 7 but they use the same controller, so i dont think it’s gen specific, but mine does not behave this way. I have 4013 set to 16 and my DHW works fine up to 30 degrees and higher.
Maybe there was a bug in earlier firmware that has been patched out.
If you’re still in warranty, contact your installer or Samsung directly and see if they’ll send someone out to update the firmware or send out a new PCB.
You can hire the tool from OpenEnergyMonitor (Samsung MIM-C02N S-NET Pro Dongle - #21 by glyn.hudson) to update the firmware yourself but it’s not entirely risk free. @SarahH managed to brick her controller doing this.