I just can't for the life of me remember. We were setting up IPSEC for a VPN along time ago and added IPSEC that has always caused 1091 1085 errors. We are not using it so I would like to remove it but cant find where.
If it's a DC, it doesn't have local policies, so this has to be managed by a domain GPO.
You should find the GPO which is setting this and edit/disable/delete it.
Inside the GPO editor, you can find IPSec settings in Computer Settings -> Windows Settings -> Security Settings -> IP Security Policies.