This is likely an RMM software forcing this.
Problem with WSUS settings
I have one Upstream WSUS server and three Downstream WSUS servers. They were working perfectly, however, one Downstream WSUS server started to change its configuration automatically, for example in "Update Source and Proxy Server" in the "Synchronize from another Windows Server Update Services server" option. The name of the Downstream WSUS server is set and also selected as "This server is a replica of the upstream server". After 30 minutes, the configuration change occurs, removing the option to replicate the upstream server and pointing to itself as an upstream server. What could this be? Is there any GPO setting to set this change?