Monster spawners are unreliable
monster_spider etc. wont reliably spawn monsters when monster_appear flag is set.
Also the spawners themselves seem to be restricted by the moster spawn delay which makes no sense when you want to have fine control over spawning monsters.
Respawning dead monsters by a button works sometimes but the monsters break sometimes making them unable to respawn at all.
Workaround: You can spawn monsters with target_spawn like this:
message "origin $self.origin classname monster_spider spider_type 1 monster_moveflags 3 target_range 1024 target monster_dead spawnflags 68 $ spawnfunc_monster_spider"
And the count of that entity to restrict the spawned amount per item also works well. Would be nice if the nomal spawners would work just as fine.