You can use the following command to list some configuration related to it
show run webvpn
Under the shown configurations you could change the used port for those VPN connections though it would naturally have an effect on your users in the sense that they could not use the default HTTPS port of TCP/443.
If you are not using SSL VPN then I would guess this might be a bug. I did have a situation on my ASA5505 that prevented from doing Static PAT for a certain port suddenly with the same error message but a reboot/reload helped in that case.
You can also use the following command to see if the ASA is using the mentioned port still for some reason
Login to the FXOS chassis manager.
Direct your browser to https://hostname/, and log-in using the user-name and password.
Go to Help > About and check the current version:
Check the current version availa...
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...