Ken - I think it may be simply the yeast dropping to the bottom of the keg. I had a keg kick recently that was a Nova lager and it had a noticeably larger yeast cake as compared to recent Diamond lagers.
I use floating diptubes in my fermenter, but not in my serving kegs. The beers are racked typical around a week in and then held for at least a couple weeks or more before tapping, so they usually clear well after the first half pint. This was true on all of the comparison beers….The only difference was the trub left at the bottom. Maybe Nova doesn’t compact as well or as quickly?