Help needed. Not properly working boka with propane burner

[der wo]

I don't manage to help a member in the German speaking forum and his English is not good enough (he says that). So I ask here for him.

Just a normal 2" boka with scrubbies on a 30l KEG and a propane burner. An added reflux return, which perhaps cause some problems but not all problems.
I never distilled with propane, perhaps that's why I can't help him.

The main question:
Why does he get with this heavy burner only such little steam?

Here a picture:

anlage317.jpg

Here a video. Water run with maximum setting on the burner, without column and packing and without the reflux return construction, only the normal slanted plates:

When you look at the flame, is this maximum? The burner has "8.8kW".
With open valve he gets 240ml per 5min water distillate. No reflux is visible through the sight glass. No leaks. Is that normal? Here you can see, for 239ml per 5min 1.7kW would suffice:

Screenshot (5).png

Of course 8.8kW propane is not 8.8kW in the boiler and he looses much without any insulation. But so much?