If you are saving every "hour" then proceeding to do more work to your project without saving
it again ! What do you expect? (Magic!)
SAVE before you close the program. (and SAVE A COPY) before you close the program.
Some times I work all day long on a Project, and save my work many times, to find out next day that all work done was not saved.
I don't think that a normal behavior of any Software.
Even if I save a Copy of the project (not all the time) if Project File exist before it will not be saved to.
I can't point went this problem occur, but I for short this behavior only happen on files that exist on my drive .
Are you saying that ...your last save does not open again , exactly as you "last" saved it?
Are you also saying that if you save a copy...it does not open exactly as you last saved the copy?
FWIW. When I Save a copy (to make a backup of the project) ...I save "over" the top of an existing filename. How do you do that?
Yes, is like you describe.
To make a backup copy I save my project with a new name, this way I create a new Project File (with no problems), This problem appear only on project that have files (projects files) already saved on my drive before.
Strange thing is that this problem appear randomly, that mean some time the problem don't appear and some times it those.
All I can suggest is delete every "temp" file in your system except the ones on the current date.
Type %temp% into the Explorer bar then start deleting.
I do this at least once a week.
Maybe start a Brand New matching project. (NEW name.ppj) then import the old one in. Once its confirmed working ...delete the other(s) .ppjs... or archive them out of the system.