Getting ready for a month long trip, and just got the trailer out of storage. Proceeded to start the sanitizing process. I bought a cheap 2 gal. watering pitcher that I use to premix the bleach in - the spout makes it easier to pour into the gravity fill port on my trailer.
Surprised to see bits of "stuff" floating around in the pitcher. Ick! Dumped that batch, and made new. Even more stuff! Blamed it on the pine trees I was standing under. Moved away, and this time even more stuff!
I need almost 100 ft of hose to get from my house spigot to the trailer, so 4 lengths of hose. Finally started testing each length. 2 were my pricey fabric collapsible "Zero-G" hoses that I really like. About 4 seasons of use. The other two were old Camco white ones, one at least 10 yrs old, usually relegated to emergency use only.
Yep, of course it was the Zero-G's that were putting out "chunks". Bummer. Long flushing, etc. just made it worse.

Bought what was available locally since we leave very soon - cheap white ones, with the bad fittings which are prone to leaking. If there is time will try to pick up new ends for them, and replace with better....

In any event - as part of the sanitizing routine, I'd advise just doing a bucket test as I ended up doing, before just trusting what your hose may be putting into your tank/plumbing. Now I wonder how long this has been happening....at least I use a filter just before it enters the trailer when on city water!