PSOS fails authentication on second file. Initial script is called from Mirror Sync customization script

Sequence:

1. Sync from Spoke ( File A ) to Hub ( File B )

2. MirrorSync customization script on the hub ( File B ) has conditions in the "DidUpdate" and "DidInsert" sections which makes a PSOS call to a script ( File B ) which processes that record telling it not to wait for completion. This allows the process to run asynchronous, and allow for a faster sync.

3. The last step of the script running under the PSOS process is Perform Script of a script in a second file ( File C ).

Error from that script step shows in the log: 

Timestamp	Information	645	sync	Schedule "ScriptName - userName 5" scripting error (100) at "fileName : ScriptName : Perform Script".

I have tried this with all running Full Access just to rule out permissions with no luck.

I am aware of this bug which was reported to be fixed in 13 v2. - http://forums.filemaker.com/posts/29d7118497?page=3

Everything else that is supposed to happens as a result of the PSOS is working correctly.

I hope someone has some insight.

Thanks,

Drew