The old Britney Spears is back — and it may get her booted from X Factor!

Insiders say the star has been for months showing signs of her old, crazy behavior.

A source says, “She shows up late, she wanders around aimlessly, and she is in her own world. She wasn’t ready for this responsibility.” The source adds that Brit has let down Simon Cowell, who expected her to bring in huge ratings for his show. That, of course, didn’t happen. Now the singer, who earned $15 million for her first season as a judge, is rumored to be on the verge of losing the high-profile gig.

Brit’s latest downward spiral allegedly began months ago on the set of her perfume ad, where she made a bunch of strange requests. The source says, “First, she wanted the producers to fly Vanilla Ice in to duet with her, which was just weird. They called him and he wanted $500,000, so that wasn’t going to work. Then, she demanded that exotic animals be flown in to be in the video and they had to tell her that that wasn’t going to work for legal reasons and insurance reasons. She wanted to do her own makeup, and when she would get it done, she would just mess it up on top of what they did.”