Responsive Service, not completely happy with prints on dark shirts.

I love the overall service from Sticker Mule, orders are processed quickly and the support team responds to inquiries and works hard to correct any issues. My first few black T shirts from them came out great, but lately, black and dark-colored shirts come with some sort of residue on the shirt. I am told it is a some sort of non-stick coating, which I understand, but it is visible on the shirt front, and changes the texture of the fabric. Washing the T shirt inside out as suggested, and the residue does not wash away after 3 wash/wear cycles. After the third washing this texture is softer, but the fabric is now wrinkled, so it looks a bit worn until it stretches back out. Would not reorder on a dark T shirt.