Perhaps not a problem for actual users, but it suggests that the newly-added witness is missing from some internal data structure.
I just added a new witness (using Link to T-PEN). There is a remove check-box next to it, but when I click the check-box, the confirmation dialog says "Remove from edition", and clicking the OK button has no effect.
I should have checked here before sending out that email. This sounds relevant to the problem I had trying to import from T-PEN, clicking the check-box, then import, but with no effect.
data tracking trouble. fixed.