SP - tung oil takes about 10 days to dry, but about 21 (more if
applied fairly heavily) to cure out. You know the drill, depending on
how humid it is, how hot it is, etc. Since tung has little or no
drier in it (compared to BLO) it dries at its own speed.
I am thinking that the tung is your problem. The uncured oil spoiled
your finish by trying to outgas under your shellac. Even shellac
can't bridge over larger areas of oil, say bigger than a carpenter's
pencil sized dot because the two products are not miscible. The
alcohol/shellac will simply sit on the oil, and not bite in. Although
it bridged at first, you can see the deterioration.
I had this happen years ago when I started refinishing, and
incorrectly diagnosed the problem as a contaminated surface. I guess
in a way it was, but that wasn't the culprit. It was incorrect
procedure. Unfortunately, I repeated the procedure a couple of times
before I found out it was me, not the materials, not the applicators,
not the wood, and not the procedure.
Oils of any kind over tropicals can be problematic. The grain
patterns on some can be very dense and then less than that without
changing much in appearance. With that in mind you can see how that
would affect the amount of oil that would be absorbed into the wood,
as well as how quickly it was absorbed.
Although I appreciate the beauty of real oil finishes, since they
provide very little protection to wood, I don't use them myself. I
don't like the inconsistency when using them as a finishing protocol.
I like predictability, and with so many other high quality resin
finishes out there that mimic the appearance of oil but have a more
repeatable outcome, oil is off the list.
As a suggestion for the fix, you might be in a bit of a pickle. The
wax will leave behinds silicones, oils, bee's wax and carnauba
residue. Your efforts to refinish will be hampered unless you get off
the wax entirely, so in my opinion that means a stripping.
If you try to simply sand it off, the heat from sanding and the
swirling motion of the sander will simply grind the above mentioned
components into the wood, and compound the problem. When you apply
your top coat, you will have similar results as you have now, but from
a different source.
Personally, I never, ever, put wax on anything. Thinking of
refinishing or finish repair, it makes it significantly harder to do.
Strip it, clean it down with a lacquer thinner bath and start again.
As always, just my 0.02.