There are two problems here:
1. the undeathinators at the spawn stations (2 2 2) are not working
1- get there press R on them and you wont see a green box for spawn point set
2- on suicide you will not spawn at that undeathinator
2. the spawn at a placed undeathinator isnt working properly
1- place a station and a undeathinator on it (best only the first station block with the undeathinator)
2- save your spawnpoint here (you will see the confirmation message)
3- suicide and observe your respawn point
4- place a core as marker and suicide again
5- you will respawn away from the core on a line with the undeathinator ... this continues without end
6 this is mostlikely a side effect of the fix for the item drop on death bug T196