Here is what happened. I was checking what other managers were offering because I am looking for a 4th starter. I checked one of the players on the trading block. When I clicked the X box in the top right corner, I got an error message but it went back to the regular screen. I put one of my players on the block, changed my starting rotation and went to submit my roster changes. Here is the screen I got:
Afterwards, I closed out of the game completely. I then reloaded, checked that my changes were still there and uploaded without a problem.