Came to say the same thing. I've had the bug happen both times DS9 dropped down to 0%, but everything has been fine whenever it didn't. It'd make sense if letting DS9's health drop that low would be a fail condition, but there's nothing in the mission itself to indicate that this is something you need to prevent from…
Well at least it's not just me! Same issue here as well, waited on the server maintenance to see if that made a difference but no dice. Glad it's a bug though, and not just me being old and missing/forgetting something super obvious from the last time I ran the mission...