I've tried uninstalling and reinstalling After Effects, but the same problem keep occurring and it only happens when I try to reopen a project. If I'm just starting a new project, everything works fine.
I'm working on a Mac (OS X 10.11.6) with version 13.7.2 of After Effects.
Try importing that project into a new one. If that doesn't work, try installing version 13.8.1 (CC 2015.3 release) or 14.0.1 (the CC 2017 release) - making sure you untick the "remove previous versions" option in the "Advanced options" section of the CC app and see if the project files behave in any of those versions.
Did you ever fix this problem? Did Szalam's advice assist you? Still need help?