Quest upload : "Sorry, we encountered a problem while processing the file you uploaded." No error.

We started getting this today, uploads are repeatedly failing at the same point when it tries to fetch a previous build of an OBB:  It says "Error" and stops the upload, but the ovr_platform_utility is not returning an errorlevel, so our build system does not know it failed.  Any idea what causes this?  Is there some other way we should detect errors from the ovr_platform_utility?

fetching previous build (2 / 4)

ERROR: Sorry, we encountered a problem while processing the file you uploaded. Please try again later.