Thumbnail saves incorrectly

[GreatTA1998]

Steps to reproduce: On the "New Post" page, I'd create a long animation (and use erasers often). When I press submit, the blackboard is overlayed with the thumbnail (which is what our current implementation does), except it looks horrendous because everything is slightly offset, so the resulting thumbnail looks horrendous too (see screenshot).

Consider the option to redesign/rewrite the implementation for saving the thumbnail so that it's safe for all edge cases.