fluzz: Acually it may do. Depending on the way as the process is handled, the
end_dialog() function may start working properly, once again.

I didn't tested, but I doubt that it was fixed by commit 1812d (it's doc change).
This error, actually, is pretty weird. We open a lot of dialogs, and keep
opening/closing them, in rapid sucession. Depending on how NPC function is, that
amount of open/close may eventually cause overrides on variables and functions.
( I mean, we are running Tania dialog, then we switch to Pedragon with Tania
dialog still open (if I'm not mistaken) then we return back to Tania dialog, and
we keep on this messy sequence, making different outputs, depending on how you
did it. )

I already encountered some variations of this bug myself. In some Pedragon
didn't started talking to me and I had to click him, in other everything went
fine, and in another I got stuck with no option while inside Tania's dialog.

I must agree with fluzz. This part is too messy (I'll not use refined words,
like 'complex'). In fact I still remember when 'Tania's sanity' quest didn't worked.