Vela incident, Nuke explodes 1979

The arguments about the Vela explosion mostly centre on the possibility of an atmospheric nuclear test by South Africa and/or Israel. Now I don't really believe SA had anything to do with it as their program doesn't seem to be advanced enough at the time. Israel maybe but unlikely without the support of SA given the supposed test site. Now given the revelations about various other things potentially far damaging that have come out since the new regime in place there I think likely that any SA involvement in such a test would be public knowledge by now.

I did note however in
this link
That SA papers at the time thought it may have involved a Soviet Nuclear Sub, add this to the statement by the hydrographic people that that the explosion occured on or just below the water and I wonder how realistic this could be given the Soviet subs penchant for accidents at the time. Does anyone know of any further research on this possibility?