This might be due to memory issue. Have you checked the memory availability in ASA?
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.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...