It is possible I didn't get it all when I cleaned everything. To clean the hose I disconnected it from the regulator and removed the schrader valve then blew it out really good with compressed air. The line blew clean and I don't recall any stuff coming from the hose. I wasn't comfortable putting any cleaning agents (like brake cleaner, acetone, alcohol, etc.) down the hose as I wasn't sure how they would attack the rubber.
I don't remember ever seeing anything on the inlet of the hose or on either side of the regulator. It's all been further down stream which I figured was due to the orifices and smaller restrictions catching the stuff (like the schrader valve and jets on the burners).
I'll likely end up replacing the hose but I will sleep better knowing what the real problem is before I do. I'm trying the 'free' options first. If everything points to the hose then I'll likely split it lengthwise with a razor blade and inspect what's inside. I also want to run my 10# tank on the skottle to see if that poses any problems. I have other means of cooking so it's not a show stopper for us.
It would be nice to get that special partner fitting mated directly to a 1/4 npt fitting so you can use whatever hose you want. If this is something that needs to be replaced every few years then I won't have to go back to partner every time.
Curious to know if anyone else has had this issue. I can't be the only one out there.