OK, it is now fixed
Just as I thought, in the very beginning of the map load, there are great chances that no spawn point are available from nearly the 8th bot join.
And the real cause is the telefrag !
On all possible spawn points, telefrag would occur so that is why no spawn point is elected.
I mainly permit telefrag on spawn,
only in the worst case no spawn points are available.
Add "+set developer 1" and you may understand
Either way, allowing telefrag is better than having a non responding server, isn't it ?
Oh, and now it is on the bleeding edge version.