I ran into this problem several times. I have a stroke on a face that I cannot delete. I try to adjust the thicknesses graphically or manually but it always remains distinct.
I made a video which may be clearer.
Has someone already had this problem?
I have come across this issue from time to time. Seems that both surfaces relative to each other are near zero, although the numeric display shows zero. You can try to use Replace Face to see if that moves one surface to the other. I have also done this as a workaround- slice off a piece 90° and then extend it back where it needs to be.
Great workaround thanks Mike