Summary
Problem1: Generator feed-back
Cause: Gridcode (Germany) & LOM type B enabled for AC-IN1 (where the Generator is connected. Symptom was that there never really was any demand on L1.
Solution: Disable LOM on AC-IN1
Problem2: Generator was not demanded beyond 4A per Phase, although AC Input current limit was set to 7.5A
Cause: Unknown, probably firmware bug in either Quattro 469 Firmware or the 2.60 Venus Firmware
Solution: Wait 3 hours, turn Generator on again, then it respects the AC Input current limit again
Problem3: Dynamic current limiter does not work (description see below)
Cause: Gridcode enabled
Solution: Disable gridcode, thanks to @Daniël Boekel (Victron Energy Staff)
I would have expected a Gridcode to apply only for the AC-In defined as "Grid" and not for the one defined as "Generator" (and I still do), but as the genset functionality is more important for our off-grid installations, disabling gridcode altogether is an acceptable trade-off.
So the question is why. I would have expected the Quattros to pull the defined amps from the genset symmetrically on each phase and to juggle real-world consumption (or excess) on AC-Out.
Instead, I see a constantly skewed L1 with feedback to the genset - see picture.
Evidently the Fronius (Symo 6) has something to do with it, because when that thing is turned off, the feedback is gone. So I wonder what's wrong there or if it falls into the "It's not a bug, it's a feature" category.
Moreover, the generator runs less-than-smooth. All load changes seem to go directly to the genset, instead of being compensated by the Quattros (power assist or whatever), so the genset Amps go up and down like a kangaroo.
I would assume that defining an AC-IN source as "generator" means that "feed-in" is an absolute no go for the quattros. So why isn't it?