With ISP Redundancy then if you want it to work then all of the Hide NAT should be configured as Hide Behind Gateway.
I believe from your update
When I change the Network address Hide to the Gateway and the main link to the backup link, there is no NAT mapping error.
That you have specified an IP address to Hide behind when you have the issue?
This is an incorrect configuration. If you configure the IP of the Primary Link then that setting is NOT updated by the ISP Redundancy and so will continue to NAT Traffic with the IP Configured.
ALL Hide NAT for it to work with the ISP Redundancy needs to be configured as Hide Behind Gateway in which case as you see then it will start to NAT with the Backup Link IP of the Gateway as the NAT when fail over.
http://supportcontent.checkpoint.com/documentation_download?id=12314
How to configure ISP Redundancy - Does seem to be very slow