There’s been a few threads on this and zero suitable solutions.
When I alt-tab away from my Unity project and then tab back to it, Unity declares that ‘the scene has been modified on disk’ and that I can choose to reload it.
Every time, without fail.
Worst still, in projects with many assets, it will import them. Then reimport them. Then reimport them. Checking the files in explorer reveals no changes.
What could be the interference?
I’ve disabled Windows Defender, tried closing any revisioning systems and reinstalled Unity3D. There must be a direct cause.
(Using Windows 8)
PostScript: The problem vanished overnight. Sorry to anyone else who has the same problem in the future, there may be clues in this thread and comments.
PostScript 2: The problem resurfaced after a number of weeks. Going to attempt to reformat and reinstall. Sigh.
PostScript 3: Solved it. My project was on a partition which is formatted as UDF. I moved the project files to an NTFS partition and the problem vanished.
Have you tried turning on Meta files? In Edit>Project Settings>Editor and switch version control to Meta Files…
If you’re working with git, remember that it doesn’t track empty folders. If you’re working with meta files, you can see those .meta files being deleted and added continuously because someone is tracking an empty folder that actually doesn’t exists for git (so Unity will automatically delete those .meta).
Disable git plug-in in MonoDevelop. It’s a pain in the ass, and it’s most of the time the responsable of those slow file loads (5 minutes waiting to open a new .cs you’ve created on Unity? no more pls…). This most probably won’t help solving the main problem, but will make your life easier. I work via command line and I’m very satisfied (however, git for windows is somehow nasty). There some git GUIs out there for Windows too.
If you’re using text-mode serialization (YAML format), lots of assets can get re-serialized (same content, different object distribution inside the file).
Mecanim serialized FSMs (.controller) get reserialized quite often in our project with no reason. Also terrains show modified, and even scenes that we haven’t touched but Unity says they’re modified. I’m quite sure this is most of the time because of third-party libraries that somehow doesn’t handle hideFlags and some other serialization stuff that well. Other times, it seems it’s a Unity bug that causes this re-serialization to be performed.
Also permissions were a problem for us in a Windows 7 machine.
I’ve been working extensively with git in a personal project for quite some time (no third-party libs), and it’s a pleasure (I’m working with lots of branches, rebasing and merging big time. No problems if I follow the empty-folder rule I’ve stated before).
Anyway, we couldn’t get to find a real solution yet nor a thread talking about it but this one.
I don’t know why… but to fix try Edit>preferences and maybe turn off auto-refresh
I recently had this same problem. I deleted a folder, and although the entire folder appeared deleted in the unity project view, it kept reimporting. Turns out I had .pdf file from that folder still open, so it was locked. Closing the file fixed the problem.
I had a similar problem with assets being endlessly reimported as a result of working on both a Mac and a PC. I did my development on a Mac, but then did builds on a PC. I used rsync to keep the two machines in sync, but every time I updated the PC, all of the assets would get reimported, even if I made very minor changes. The work-around I discovered was that if I didn’t update the Library/AssetServerCacheV3 file on the PC during the rsync (either backing up and restoring the existing file or using the --exclude flag), I could avoid the reimport.
I see this is an old thread, but I mentioning this in case it’s useful to someone else.
Watch out for symlinks, i had to delete one of mine to fix this kind of issue.
I Had similar issue and none of the above worked for me.
Issue: Imported a particle plugin from asset store and since dint find a need tried to delete it but it kept coming back over and over after every delete operation as if my system was pocessed;)
Tried all the above: dint work
tried renaming before deletion :didnt work
Started deleting files individually and finally found one file that was causing the issue. It was the import setting file of the plugin. It says clearly that “Once a native plugin is loadedit is never never unloaded … blah blah blah…”
so i manually deselected the platforms and deleted the folder and it worked!!