Hello,
you could be hitting the bug below. Try and configure:
set security-association lifetime kilobytes disable
on the affected spoke...
Bug Details:
DMVPN Spoke stuck in IKE state after heavy traffic
CSCtq39602
Description
Symptom:
DMVPN Tunnel is down with IPSEC configured. The show dmvpn from Spoke shows the state is IKE.
Conditions:
After heavy traffic was pumping from DMVPN Hub to Spoke for some time, from a few minutes to a couple of hours.
Workaround:
Configure ''set security-association lifetime kilobytes disable'' to disable volume based rekeying will reduce the problem.