When a machine moderates content, it evaluates text and images as data using an algorithm that has been trained on existing data sets. The process for selecting training data has come under fire as it’s been shown to have racial, gender and other biases.
It’s been shown over and over again for the last two decades that you can’t build a reliable archive on platforms outside of your control. Stuff like Instagram can be useful for trying to draw traffic to your own platform - but you always should treat those platforms as throwaway content.