OK, I used decals once on my first project, the Testors sheets. that was 2 years ago, and I didn't have a working printer, so I used my buddy's HP inkjet. Perfect results. Today I tried the new Epson inkjet I bought recently and I get vertical streaks. Image prints perfect on regular paper. Tech support from both companies was rather lacking, to say the least.
Who Uses decals, and what setup do you use i.e. file type, operating system, printer.
Needless to say, I am quite miffed.
Maybe try playing with the paper type if that is an option for the print? Try variations of 'glossy' or 'photo', etc, and see if that helps.
I will usually use the glossy or photo setting with mine.
Make sure you have a clear path through the printer, and that the paper isn't getting pushed up into the jets as it prints.
I sometimes get those vertical stripes, sometimes cleaning the print heads will help - the printer utility usually has some button to do that.
Also check you have the decal paper that is for ink jets, as I'm not sure what would happen if you use the laser decal paper in an inkjet, or visa versa.
The biggest difference between laser stock and inkjet stock is that the laser won't likely get a clearcoat after being printed so it's a tad thicker to compensate. Inkjet stock has less medium because you're required to seal the ink with a topcoat of decal film or clear paint to seal it before you get it wet.
If I recall the Testors comes with a can of topcoat and I think they've only ever made inkjet. I've never had great luck with inkjet, although it is more common. Once the price of color lasers became more reasonable (although the first time you need the 4 toner cartridges it takes your breath away) I got one and have had much better luck.