After some PS operations are completed, e.g., dense point-cloud or mesh generation, the drop-down menus are grayed out and aren't functional. This happens intermittently, without any apparent reason. The console generally just says the operation is completed with exit code "1." The only way I've found that allows me to access the menus is to use the "quit" PS drop-down command, and then cancel when the pop-up menu appears asking if you want to save the project before quitting, or to use the save button. However, if for some reason you don't want to save the result of the last operation, don't "cancel" in the middle of the save--you will likely lose your photo-alignment, point-cloud, and mesh, or render the model unreadable.
Another issue I found when working on a model stored on a portable hard drive is that if you save a project to a drive that runs out of space, PS doesn't warn you that there isn't enough space on the drive and doesn't inform you that the model hasn't saved completely. I thought I had saved a project, but when the next operation ran out of memory and PS crashed, I had to reboot the computer. Only then I found out that the last save wasn't completed and the project file couldn't be opened, causing a loss of three days' of work.