Hi,
RFC communication error can occur in various levels
1. When Gateway HUB connects to BEP system
2. When BEP connects to ERP System
3. When BEP connects to Other Data source such as BW system
I think you need to find where the the RFC communication is failing. For that, the best option would be to check the stack from error log transaction. This will help you to identify the reason of the error.
Regards,
Atanu