Ok, cause if it is the exact same crude, and the distillers put out the exact same product, and only one distiller’s product oxidizes, then one distiller is adding a step.
Does the offending distiller give you less dist. in trade for your crude? I think he is degumming and leaving the solution slightly acidic.
That’s about all the info I have for you my friend, you can search “quinoids”. A word of warning, that rabbit hole is dominated by the phd savages here, and you’ll need to use google to translate every other word… at least i did 
Other places that need tagging are the red ring of death thread and the color thread
They all point to the same quinoids. We used to think it was CBN before @Photon_noir came around with his data. My last word of warning is this is all relatively new and experimental, so no one here or in the wild can give you a definitive answer on what they are and how to stop them until we all have more data.
The only guy I knew about that focused on this is now dead.
The only quick fix I can think of, is putting your carts in the vacuum oven and loosely putting on their silicone tops and drawing vacuum. When the vac breaks, they should suck down and hold a weak vac inside the cart till your customer gets it.