Have the server sync sv_respawninsurvivalinvasion so clients know of its value.
In response to https://zandronum.com/tracker/view.php?id=4283#c23939, when sv_respawninsurvivalinvasion
is changed in survival invasion, the server will now tell the clients the status of the CVar and whether or not spectators can respawn at the end of a wave.
Edited by Adam Kaminski