90% of our business is dark shirts and they seem to last longer than our white shirts.
I am gonna say its pretreat and heat press timing.. Do you happen to know any professional painters? ones that use paint guns for a living..
I know its a weird question but my partners close friend is a professional painter and we couldn't get the hang of the pretreat (Wagner gun) our shirts were coming out like yours are. He came over adjusted the gun and showed us a few tricks and ever since then its been a breeze and our pretreat problems are gone.
Also, we had a professional painter in our
DTG class and he was the only one that got it right on the first try. Its worth a try cause I feel that class wasn't long enough to teach the proper pretreat techniques and its really something that can't be taught over the phone.
I hope this advice works for you...