November 27, 2019 | 8:14pm

NBC insiders are puzzled by a sudden slew of stories about Gabrielle Union’s allegedly terrible experience as a judge on its “America’s Got Talent.”

Union was let go from the show last week — along with co-star Julianne Hough — after a year of appearing as a judge.

On Wednesday, both Variety and Vulture published articles detailing a “toxic environment” at the show and alleged racism on set.

Both stories quote sources who said Union got notes from staff saying that her hair was “too black,” and claimed that the actress had complained after Jay Leno appeared as a guest and joked that a painting of dogs looked like something “on the menu at a Korean restaurant.”

But a confused NBC insider said that Union had a “productive conversation” with producers about the Leno incident at the time and was surprised that it was coming up again.

Meanwhile, a network insider said the notes on her hair were only about “hair continuity” for both Union and Hough.

A show source told us: “A half-dozen ‘AGT’ employees were asked [about the ‘too black’ notes] and no one had heard this. I would honestly be shocked. Ensuring a safe environment is so important to the show. Anytime someone comes forward and has issues, we take things very seriously.” They pointe