[Zubersoft]

The error is caused whether not any custom stamps are used unfortunately, because the code first tries to obtain this folder before checking both libraries to see what stamps need to be either sent or downloaded. If the stamp folder does not exist, a null reference is returned, and then the code proceeds to use the reference which throws an error and aborts the sync due to that. So the fix is easy - I only use the folder reference if it's actually required due to the use of custom stamps. If no custom stamps are used, then it's perfectly fine if the folder does not exist. 

You are very welcome - thanks for reporting the issue in detail and giving me everything I needed to investigate and fix it.

Mike