I have a wooden exterior door on my house (oak). I stained the door
and then put an exterior polyurethane sealant on it (5 coats).
Moisture must have gotten under the sealant because some black stains
have appeared under the sealant, to the point where it must be redone.

I'm in the process of stripping the polyurethane and that's going
pretty well.

My questions a

Once the sealant is off, does the door have to be sanded down to the
bare wood (remove all the natural oak stain that I originally applied?

How to remove the black stains?

What to reseal it with?

Any suggestions?

Stephen

P.S. We are in Florida, near the ocean (not the greatest location for
a wood door, but several neighbors have them, and they've been able to
have a wood door, as long as it was well sealed?