I wouldn't say this is unique to Andrew Yang and his campaign. I had a ex-coworker travel from California to Texas to work on Beto's campaign in 2018 and when she came back, she had the same stories of minimum wage/volunteer workers being treated with abuse and that abuse and misconducts ignored. The campaign eventually did get around to making things right, but it was too late and she had already left Texas.

Memorable quote was: Mistreatment of campaign staff is common (I think for similar reasons as artists and video game programmers often get abused? the short-term pressure and passion project nature encourage exploitation)