Asset with GUID __ has empty path but has assettimestamp???

Hi guys, I've just upgraded from Unity 5.4.0f3-HTP to Unity 5.4b4 and I'm getting 3 of these errors every time I open the Editor.

"Asset with GUID <***> has empty path but has assettimestamp???"
with 3 different GUIDs.

I've had these before and normally they go away after an Editor restart or re-import.
I've tried re-importing the library, deleting all but Assets and ProjectSettings folders and re-importing and all have no effect. I'm guessing there are 3 assets that are causing this, but I can't tell which they are or how to fix it.

I have a few third party SDKs in the project which do some asset modifications on load. Plugins being set to Editor-only etc. But these didn't have any issues in 5.4.

 

@unity_chris unfortunately I won't be able to upload the project as it's confidential. I'll work on making a cut-down repro next week.

 

Did you ever get a project that has that error? If not I have a one I can send you that is doing it.
-Robby

 

I'm also see this in a project that was just upgraded from Unity 5.4.0f3-HTP to 5.5.0b5. It disappears when I delete the library, but then reappears the next time the project is opened.

Unfortunately, I haven't got a minrepro yet. I can confirm that none of those GUIDs appear anywhere in the Assets directory (grep returned no results). Is there anything else I can poke at to try to diagnose the bug?

 

Relatedly, there are files in the library which correspond to those GUIDs:

There's also this warning:

 

Finally managed to make a repro, sorry for the delay.
Bug number is: 837519
I managed to narrow it down to the EditorSettings.asset. I systematically deleted files from the project, leaving no Assets remaining. After deleting ProjectSettings files one by one. Leaving EditorSettings.asset in causes the error, while deleting it removes the error.
The error also disappears if I delete my Library folder on this cut down project, but if I do that on my main project, this doesn't fix the error.

UPDATE: It does fix the error if I delete my Library folder AND delete the EditorSettings.asset.
But deleting just one doesn't fix it.

 

I got a reply from the QA team stating that:

"For now there is a workaround for the issue you are facing.
Navigate to assets and reimport all assets."

Unfortunately, this only works if Asset Serialization mode is not set to Force Text.

 

Is there a workaround to this when using Asset Serialization with Force Text?

This is making me crazy. I have some prefabs that are always losing references because of this error.

 

I think it stopped doing it (on b10 now) but I can't confirm if the underlying issue has been fixed or the asset(s) in the question have been removed / fixed. I get a whole host of other errors on Editor startup anyway, so they may have just fallen into the background.

 

@LeonhardP This is bad! Is there some workaround for this?

 

Still does it on 5.5.0 RC1. Seems that the errors with b10 were masking these ones.