Intermittent sandboxing error

I'm experiencing an error (denied file read access) about 25% of the time I try 
to extract certain large RAR files (5-10 GB). If I queue several of these files 
at once and one of them fails, all of the subsequent files also fail for the 
same reason after extracting only 50 MB. I am able to restart them individually 
and they generally succeed.

I'm extracting to and from an external USB drive with 777 permissions and 
ownership ignored on the volume. When the error occurs, I see this sequence of 
logs:

------------------------------

4/29/15 10:11:57.599 PM The Unarchiver[18067]: view service marshal for 
<NSRemoteView: 0x10032d4a0> failed to forget accessibility connection due to 
Error Domain=NSCocoaErrorDomain Code=4099 "Couldn’t communicate with a helper 
application." (The connection was invalidated from this process.) 
UserInfo=0x1007208b0 {NSDebugDescription=The connection was invalidated from 
this process.}
timestamp: 22:11:57.599 Wednesday 29 April 2015
process/thread/queue: The Unarchiver (18067) / 0x109d81000 / 
com.apple.NSXPCConnection.user.endpoint
code: line 2972 of /SourceCache/ViewBridge/ViewBridge-46.2/NSRemoteView.m in 
__57-[NSRemoteView viewServiceMarshalProxy:withErrorHandler:]_block_invoke
domain: communications-failure

4/29/15 10:11:57.000 PM kernel[0]: Sandbox: The Unarchiver(18067) deny 
file-read-data /Volumes/incoming
4/29/15 10:11:57.000 PM kernel[0]: Sandbox: The Unarchiver(18067) deny 
file-read-data /Volumes/incoming
4/29/15 10:19:23.780 PM lsboxd[221]: Denied process 18245(UNKNOWN) access to 
shared list cx.c3.theunarchiver.LSSharedFileList

------------------------------

I haven't noticed this problem when doing extraction on my startup volume, but 
it might very well occur there, too. I'm on OS X Mavericks with 3.9.1.
Original issue reported on code.google.com by devin.mccabe on 30 Apr 2015 at 3:29
letup / theunarchiver

Intermittent sandboxing error #826
