Presprayed Smart Strand Silk (poly) with 2 oz / gal. (4 oz in small area), Flex with Citrussolv. Rinsed with Flex Ice at recommended dilution. Customer called a few days later about residue on her Dyson. I cleaned the scum off her vac and recleaned with the same chemistry. A few days later, customer complained about stiff carpet, so I performed the mother of all rinses (MOAR) with Fab Set, which left the carpet soft and visually clean. She called yesterday (30+ days later), about new scum on her clean vacuum. She is not trying to jerk me around. I need to understand what is causing this, not only for her, but for myself. I've cleaned hundreds of polys with Flex prespray and Ice rinse. Are some polys more difficult to rinse? (More oleophilic?) Is it possible that Ice doesn't have the emulsifying muscle to rinse this particular poly? Is Ice leaving residue? She says the previous cleaner didn't leave residue, but she didnt call him back because he was sloppy and didn't prevac, prespray, or scrub. I'm guessing he didn't even know the fiber, but hit it with the same alkali rinse he uses on everything else, which was, by chance, appropriate for this fiber. Im thinking my next approach should be a mild alkaline rinse (Point Blue, Pro Max, etc.). She also mentioned the carpet is matting. I believe this is typical of Smart Strand. Much obliged.