Enabling Allow Client Side Navigation results in a NavMesh Needs To Be Rebuilt error message on the Client

Enabling Allow Client Side Navigation results in a NavMesh Needs To Be Rebuilt error message on the Client. The Client cannot use the nav mesh.

This is a regression: this did not occur in 4.9.2 (though there appears to be a separate issue with it in 4.9). Reproduced in 4.10.0 binary. Did NOT reproduce in Main (CL# 2785572)

1. Create a new Top Down template project
2. Project Settings > Navigation System > enable Allow Client Side Navigation
3. PIE with 2 players

Result:
On the Client, "NAVMESH NEEDS TO BE REBUILT" appears. The Simple Move To used in the PlayerController does nothing (works in 4.9.2, though with some problems).