Hi,
This might be due to memory issue. Have you checked the memory availability in ASA?
210007
Error Message %ASA-3-210007: LU allocate xlate failed for type [ static | dynamic ]-[ NAT | PAT ] secondary(optional) protocol translation from ingress interface name : Real IP Address / real port ( Mapped IP Address / Mapped Port ) to egress interface name : Real IP Address / Real Port ( Mapped IP Address / Mapped Port )
Explanation Stateful Failover failed to allocate a translation slot record.
Recommended Action Check the available memory by using the show memory command to make sure that the ASA has free memory available. If no memory is available, add more memory.
And also related bug in 8.4.6 version of OS CSCub08224
You can try upgrading your ASA.... to 9.1 version or something.
Regards
Karthik