Happend to me too a couple of times.
I believe some of the rxdata got erased or something.
I didn't know how to fix that so I just restarted the whole project.
If you are in the beginning of the game and know how you made it,
I believe it is better to make it all over again.
If you aren't, make a new project and compare the files. If there is something missing, let me know...