No, nothing in the error log at all. The plugin thinks it is working fine. There is no useable data inside the archive that I can get to. Attempting to open one in Windows delivers a generic "archive damaged" message. A Mac can open it, but it contains a different type of archive, which will expand into another zip, then another... in an endless loop.
I suspect that this is not really a problem with the plugin, but more likely a problem with my PHP packages and or config. Any assistance there is welcome.