To reproduce:
1. Open attached project
2. Open Console window
3. Observe errors: "UNetWeaver error: NetworkBehaviour BaseNetworkBehavior`1 cannot have generic parameters" and "Failure generating network code.
UnityEditor.Scripting.Serialization.Weaver:WeaveUnetFromEditor(String, String, String, String, Boolean)"

Expected behavior: no errors, ability to play scene
Actual behavior: errors in console

Note: there errors can be cleared from console, but scene still cannot be played

Workaround: delete every file that has BaseNetworkBehavior in its name.

Reproducible with: 5.3.0b4, 5.3.0f2, 5.3.0f3, 5.4.0a4
Not reproducible with: 5.1.3p3, 5.2.3p1, 5.3.0b2, 5.3.0b3