My laptop isn't charging anymore lol. This will probably be my last post for now.
For the record, I haven't gotten videos working on Rewrite either. So far, there's been 2 visual novels I've failed to get videos working on (that are serious, some just fade to black and then continue on). One being rewrite, and the other being "If you love me say so". As far as I can tell, the gstreamer plugins are the answer, however, I have a really weird issue with my computer where decoding certain things crashes my computer on both Windows and Linux.
So I can't actually know that this solution works, however what I do know is that without the gstreamer plugins the game just crashes. With gstreamer plugins, my entire system crashes. So something has changed and I bet it has to do with video decoding.
If you end up looking into it further, I feel as if the gstreamrer plugins are the right direction. Maybe theres something I've missed.
You can look into installing LAVFilters, which is another common way to get videos working in Visual Novels. You might have more luck there.
For now, just having the save workaround is probably best. Sorry I couldn't help you fix this specific issue. It's got me stumped in a lot of ways too. I'm concerned that the VN might crash before it counts a route as completed (since it'll crash during the ED of whatever route you're on), though I haven't confirmed that it does or does not do that.
If you have any more questions, feel free to ask. Though, Until I get a new charger for my laptop, I'll be recalling from memory only.