Increase the polling interval of the Watcher Service to 120 seconds.
If you still get the Unauthorized Modification notice when you deploy GPOs try increasing the interval again by doubling it. You can increase this up to 1800000 which is 30 minutes.
If increasing the interval does not resolve the issue, please try restarting the Watcher Service.
Also confirm there is only one Watcher Service running in the environment.