Uncalibrated print setup

Submitted the same image for die cut stickers and DTF transfers. Stickers came out perfect, DTF colors horrible. SitckerMule kept trying to convince me the issue is that my artwork was RGB, not CYMK. Couldn't explain to them that the moment it looks perfect on one medium, the problem is not with the ark anymore its with the print process. They would not acknowledge the issue is on their side. SM offered to "fix" my image and reprint the batch. Tried explaining that manually fixing things will just result in the next batch being equally broken / other people having the same problem. Was told nobody's complaining. Ok then.