Again, I'l say, the Thanksgiving cacti can defy all my plant logic. Mine too, certain ones, have papery thin segments, others have thick rubbery segments. One would think they need 'cacti' type soil but these aren't truly cacti, but come from cool forest, right?
All I can think is they have very fine thin roots that can easily die off. One of mine did, on taking it out of its pot there were no roots.
I would not disturb this while in bloom, but may in spring, investigate the roots.
