Myself, and at least several other users have a weird issue completely stalling our RTTS player promotion progression, and as it currently sits we'll never make it to the majors.
My RTTS player played a single position for 200+ AA and AAA games (Right Field) in the Met's organization, and during my AAA time the manager comes to me and tells me that at the majors, that position is filled in the organization, but he'll see what he can do about getting me my shot.
Afterwards, my manager changes my player's position in the lineup to First Base (for whatever reason) and immediately after he did so, my player was traded to the Rays organization as a Right Fielder.
After being traded, this new/wrong position sticks - and the new manager always pencils my player in the lineup in that position (First Base). However, before the first inning in the field, my player is immediately subbed out for a defensive replacement by the real first baseman. Regardless of what changes I make to my player's settings, he is always penciled in at first base.
Looking at the roster for the Ray's AAA affiliate, and I am listed as the only right fielder, and there is already a first baseman. When I view my player details outside of RTTS, it is listed as a first baseman now. The only time I get an at bat is if we are the visiting team, and if we make it to my spot in the order within the top of the first inning.
Because of this bug, even if I sim the entire season, I get at most about 20 ABs for an entire season - thus insuring that I never make it to the majors. I've posted to the subreddit, tweeted, and submitted a bug report. Just thought I'd post here for others who may have the same issue and to see if others have been able to get out of this loop. I have more than 8.5 hours in RTTS on this save, so this sucks.
TL;DR - A bug happens that swaps my player's position, and during that swap I am traded to a team that already has that position filled, so I never get to play. I am substituted out in the first inning of every game, and because of this the most ABs I get for an entire season is about 20, and I never get to play defense.