The 10s is normal, it’s should be the time when the OSPF neighbor relationship is re-established and the route is refreshed. The OSPF neighbor relationship is established with the system master. If the active node is powered off, the OSPF neighbor relationship is re-established.
The second 30s may be caused by STP convergence. You can check whether the STP port status changes during the switchover. If yes, disable STP in system view or enable STP edge-port on the port connected to the server.