Are there any actual legal risks at all when using royalty-free content in your monetized videos, from a well known site intended for that exact purpose? Can an author/owner of the content you downloaded, ever claim any rights on any grounds at all, after they see their royalty free content was used in a video reaching - say 2 million views, but you followed all the instructions exactly as they were stated for each piece of content (song, picture, clip...) on the website? For example if they decide to claim that you used their material and if they lie about the status of the material at the time you downloaded it?
And what about if the author modifies the specs of a piece of content you downloaded and used for commercial purposes and bans the use for commercial purposes in between the time of the download and the time you upload your own content (now including theirs)... I don't know of any preventive measure against this kind of scenario... Would it be of help if I record or screen-grab the specs of the material at the time of downloading or do the sites offer some kind of proof that it was 100% legal and in accordance with the rules / specs or something like that?