Seems like a technical problem or a shortcoming of the platform, but regardless, someone refusing video evidence like that (especially from who is essentially their business partner and has little incentive to commit fraud) is unacceptable. The problem is that support is outsourced to monkeys with no real power to investigate or change things and it's cheaper to fob you off than to assign the issue to someone with at least half a brain to see what's going on and make it right.
Because like all customer-focused apps, they are focused on customer retention and satisfaction. It’s much better to let customers cancel orders or complain after the fact and just refund their money, than it is to fight with them and have them leave a bad review - or worse, have them request a chargeback, too many of which will get you canceled from your card processor.
Meanwhile, the delivery platforms just push the cost back to the restaurants.
If restaurants had the guts to cancel their service with the delivery platforms, they could squeeze them into doing a better job, but at this time no restaurant can afford not to participate in the delivery economy, at any cost.
Reminds me about an article I read years and years ago about a company that was put out of business by Wal-Mart because Walmart would take almost anything back as a return and just forward it back to the company for a refund. They described getting tractor trailer loads back with empty boxes, boxes with most of the pieces missing, etc - all debited from their sales.