Rapid Recovery restore mailbox database failed


I have Rapid Recovery 6.1.3. I protech my two exchange 2013 server in DAG mode. All the backup seems fine, the green dot is there beside each recovery point. When I try to open a database with incremental backup, I always have an error that the core service cannot be reach. please reach network connection and if the service is running. I run the local mount utility directly on the core server.

If a try the base recovery point it's open database and I can restore data. It's the only recovery point I can restore, even the next incremential after the base isn't working. I change the options in local mount utilty for the timeout for the core at 20 minutes.

I try to stop core service, restart it, reboot the server, nothing change.

All my other protected machine I can mount the recovery point without problem, it's just the incremental exchange database that doesn't works

My core service is a DL4200 appliance.with 128Gb of RAM with currently use only 20% of RAM and 1 or 2% of CPU

Can I do something to correct the bug?