I had this problem (as well as the "5 won't die" issue) & it was totally doing my head in - recurred after complete reinstall, etc.
However, after several attempts, re-fighting the whole ending after leaving the Pocket Plane, I've finally gotten through. The key seems to be that I did *not* install Oversight beforeon the last (successful) attempt, so I suspect that's where the problem lay (for me, anyway). Of course, it may have been the order of Mod installation, me being careless in previous reinstalls, etc., etc., etc...
BTW, must take this opportunity to say "Well Done, Mr. G." for creating the Ascension Mod. Despite all that bother, it *is* a much better ending than the published edition. I cried with joy & now feel suitably contented!
Might even take a break from BGII, now that I know that even Saravok loves me!
Boris the B.