Reaver Lord in Kagrumez not spawning

[Moophl]

The reaver lord or marauder in Kagrumez that is supposed to carry the two final resonance gems for the kagrumez gauntlet quest is not spawning for me. There are 2 low level reavers in the arena when I enter, and one of them speaks her part of their dialogue when my character comes close enough. The line of dialogue that should be spoken by the reaver that carries the gems is not played, and there is no pause for it - the other reaver simply says her two lines back to back (indicating to me that the lord is truly not spawned, and not just "lost" outside of the walls of the room).

-My character is level 50, so there should be no levelling reason for the reaver not to spawn. The two reavers that do spawn are of low level - sometimes two plain reavers, sometimes one of them is a reaver outlaw. Web hits indicate that they should be levelled, which might point to a problem with the game not taking my character's level into account correctly.
-Some web hits indicate that the gems could be placed on the floor of the arena if the reaver is missing, that does not seem to be the case for me. I've disabled collision and looked through the rest of the cell without finding neither the gems nor the reaver.
-Since i had recent saves, I've tried to enter the arena for the first time several times under different conditions - with either two or all three of the other gems in my inventory, with and without followers, and by walking to or fast travelling to Kagrumez. No difference.
-I'm using SkyUI but no other 3rd party mods. I have tried to disable it, which did not solve the problem.

Does anyone know of anything that will make the reaver lord spawn, or does anyone have the command needed to manually spawn him?

Thanks,