Build can't find files and crashes?

Android cloud builds have worked well for us for a while, but lately all builds are stopping at a particular point starting with "file not found" errors and then a lot of missing prefabs. I've uploaded the weird part of the build log: http://pastebin.com/hrUpkTuU

We've tried a clean build (same result), creating another project (same) and building locally from a clean repository clone (works fine). Is there some setting I've missed that could break things?

 

Library isn't checked in and I can't find anything suspicious in the commits. I suppose I could try pinpointing where it breaks.

 

Well, I narrowed it down to a specific commit that changes import settings for a bunch of sounds (metafile changes only). Weird. I'll try reimporting the sounds and building a test branch tomorrow to see if it fixes things.

 

I iterated through a few failed builds to reimport all the sounds the cloud didn't like for some reason; now it works again. Strangely enough, the log still had "file not found" errors for other sounds I didn't touch (they were also added after the first failed commit)... but it still works. *shrug*