I don't use transparent colors. I use halftones.First guesses are something to do with either use of transparent colors in file, RIP, or RIP knockout settings.
The RIP is not the issue, because as a screen-printer I know how to create the print file manually, and I have done so.
By the way... This type of design cannot be done well with screen-printed transfers either.
I've seen other people trying to do it as well, but the results are always somewhere between bad and awful.
If DTF was as good as some say, all screen-printing shops would be out of business by now.
We all know they are not.