Some sort of pre-moderation would be good as its difficult to know how the moderation system will react.
Something like “our moderation system has determined that this material may violate our terms of service and so cannot be uploaded. If you would like to contest this please fill out x form explaining why”
This way if something is genuinely dodgy and the creator knows it is they probably won’t appeal and it won’t get uploaded in the first place. At the moment it seems like roulette.