A couple of questions. What ink, paper and software are you using? What media setting are you using in the RIP, i.e., media name and resolution? I did a 7 year stint running sublimation printing production for a major promotional products company, where cost was a big thing. I have experienced this issue myself and you are definitely running into a saturation issue. My solution was I made a custom profile for my media, which was a 95 GSM paper from China, a pretty light weight media. The possible solutions are a heavier GSM paper, printing at a lower resolution (maybe), carefully making some changes in the ink setting in the RIP or a custom profile. Paper is a big factor in sublimation profiling, which is approached a bit differently then profiling on vinyl or photo/art paper.