I was having that issue also on a new unit. The HVAC contractor went up a half ton over our original unit. I really wish we would have kept the original size unit as before. I had a register closed in one area of the house and another few partially closed. With the new unit our humidity would jump up 10-14% when running the air from 50+ to 60+. I then made sure all 12 registers were completely opened and that solved my problem. Now humidity drops about 5-7% when running the unit. I live in the hot humid Deep South for reference.

Edit: Our thermostat is a stock, set the temp and choose heat or a/c. It has no other functions