These bugs were found in the most recent commit (https://gitlab.com/GameDevTV/UnityMultiplayer/RealTimeStrategy/-/commit/b101311d48b81fa41e22ab9ff157a852564010e6).
First, the base did not have an AimAtPoint set for the base and was causing a null point exception when attempting to target base.
Second, after clicking Leave Game, the host receives a null pointer exception in the OnServerDisconnect method when attempting running:
RTSPlayer player = conn.identity.GetComponent<RTSPlayer>();
First bug was an easy fix, second bug I have yet to figure out