I am not sure if this would be the case in your issue as you run a packet tracer to get it working again.
We have some defects on this code but in them packet tracer also should not resolve the issue. I still think it has something to do with the IPSEC lifetime timer mismatch or DPD as the packet tracer will refresh this timer and this resolves the issue for you.
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...