Unfortunately, that's a pretty tricky question without an easy answer.
Remember: we’re not your lawyer nor can we provide individual legal advice or instructions on managing the content you upload to your Redbubble portfolio. For this reason, we’re not able to say why a work was flagged and how you can avoid work suspensions in the future. Keep in mind there are some instances that require work reviews, like submitting a work to the Fan Art Partnership Program which you can learn more about here.
However, when your work, or multiple works, are suspended for review, there’s usually nothing to worry about. Most of these suspensions are temporary and you’ll receive an email notification once the review is complete.
Ultimately, this is nothing personal and we don't think you're a bad person (unless you happen to be one of those evil twins from an alternate universe). We can provide some general guidance and the Redbubble IP/Publicity Rights Policy is a great place to read about Intellectual Property generally, as well as trademark, copyright, fan art, and publicity rights.
Obligatory Yet Very Important Legal Disclaimer:
Don’t be fooled by any complicated jargon (and how snazzy we look in pinstripe). We are not your lawyer and this is not legal advice. We recommend contacting an attorney if you need an actual legal consultation.
Rather, this is general information aimed at giving you the legal lay of the land. While we can’t defend you in court, we know that art and IP ownership can be murky territory; the least we can do is arm you with the right kind of knowledge to get you started.