1893483 - Unable to synchronize. Client reports "Protocol error" followed by "End synchronizing subscription(s) '<table>'" - SQL Anywhere

We are unable to synchronize the MobiLink client through the Relay Server. It is working internally, if the client device communicates directly with the MobiLink server. But it fails, if the MobiLink client is connected to the internet and has to synchronize through the Relay Server. The error in the client log file looks like:

:
I. 2012-07-26 08:47:50. Waiting for MobiLink to apply upload
E. 2012-07-26 08:47:50. Protocol error
I. 2012-07-26 08:47:50. End synchronizing subscription(s) 'qqq'
:

SAP Sybase SQL Anywhere

KBA , BC-SYB-SQA , SQL Anywhere (on premise, on demand) , Problem