Sen. Kirsten Gillibrand (D-N.Y.) acknowledged on Tuesday that there were some “post-investigation” errors in her office’s probe of a former staffer’s sexual misconduct complaint against a co-worker.

“We decided that because of some post-investigation human errors that future investigations should be done by our new chief of staff, who actually has experience in this area,” the presidential hopeful told reporters during a campaign stop in Iowa, The Associated Press reported.

Joi Chaney, Gillibrand’s chief of staff since January, served on the U.S. Equal Employment Opportunity Commission during former President Barack Obama’s administration.

Gillibrand last week defended her office’s investigation of the misconduct complaint, telling reporters her staff conducted a “thorough and professional investigation” after a former female aide reported the harassment. She said her probe was “able to substantiate derogatory comments and not able to substantiate the sexual harassment,” and added: “The sexual harassment claims did not rise to the level of sexual harassment.”

Gillibrand didn’t elaborate on what she now says were “post-investigation” errors. She said her deputy chief of staff, Anne Bradley, who led the investigation, resigned following questions into how the claim was handled. “The decision was [Bradley’s] own,” Gillibrand told reporters.

Politico reported earlier this month that a young female aide in Gillibrand’s office resigned in protest last summer, saying the senator’s office didn’t do enough to address her allegation that special assistant Abbas Malik repeatedly sexually harassed her on the job.

Malik, who initially kept his job, was ousted this month after Politico presented its investigation of separate workplace misconduct claims against him.