Your plugin has a race condition. OnConfigsExecuted() guarantees that all configs have finished executing. But you're issuing an "exec" command inside OnConfigsExecuted(), and the changes won't necessarily be mirrored in plugins which rely on this guarantee (such as reservedslots).
I've added a forward to the 1.1 branch to help mitigate this problem, you can read about it
here. This change will make it into 1.0.2 or so. I won't unapprove this plugin until a stable release has the new feature and this plugin has had time to update after that.
Note: "fixing" by using OnMapStart() is not a good idea since it occurs before sourcemod.cfg gets executed.