Why is Handmaid’s Tale sequel facing a problem?

The Hulu Handmaid’s Tale sequel, The Testaments, is described as having a major issue tied to an inconsistent backstory for at least one character. The story emphasizes that the problem goes beyond a single episode and could derail the spin-off if it affects continuity or motivations across the season.

No further specifics (which character, what the inconsistency is, or how it manifests on-screen) are provided in the excerpt, so the exact nature of the conflict can’t be confirmed from this text alone.