Review ALL devices connected in your network including routers.
Make certain all devices are up-to-date.
Make certain the clock is set to only get the time from time.windows.com or 10.4.0.1.
There is a known problem with many routers. They get the time from many places even if configured correctly. You need to download the latest firmware (operating system) for your router from the manufacture's Web site and update it. After updating the router, then review the configuration. Specifically look for where it gets its time.