Unity Hangs and Reimports Substance on Stop

I think this problem started when I started making use of substances but I am not sure if that is the actual cause…

When I run in the editor, everything seems to be working fine except that the objects with substances on them are rendered in blue for a few seconds. Then their textures appear. I am using lightmaps on these if that could be related.

When I click the play button to stop execution, Unity hangs for about 30 seconds with the Mac “beachball” cursor appearing. Eventually, the import progress dialog shows up and it appears to reimport the .sbar for one of the substances in use (I am only using 3, but only 1 seems to be reimporting). After the import finishes, everything works again, but that takes a few minutes. Needless to say, this is slowing down development progress severely.

If I ask Unity to “reimport all”, the problem goes away for a little while, unless I restart or switch scenes (not sure about this exact pattern but that’s my best guess).

I am using Unity pro with GIT source control… GIT puts a .git folder in the root folder - could that be causing a problem? The project files are on my main HD - not an external drive (I read elsewhere that external drives have lead to problems with constant reimporting of assets). Also, the drive is an SSD, so it should be very fast.

I know this is a very late reply but as this was the first result I got when searching for a solution to this problem myself I thought it worth it.

I’ve found that if you have a copy of the preset in your normal scene hierarchy the delays when stopping/starting the game in the editor go away. This copy doesn’t even need to be active, it just has to be present. I’m assuming this is because it effectively lets Substance know that the textures for this material are needed all the time and so it doesn’t delete the cached versions when the game stops, and doesn’t need to rebuild them again next time it starts.