I realize this thread is kinda a snorefest but I did find something that works, more or less, to unlock the car with the remote. I found that if I first press the lock button then quickly press the unlock button it will unlock the car 95% of the time. Sometimes I may have to repeat that process but it will work. I just wish I could fix the main issue, whatever it is.
2011 GT (Mustang No. 7)