Sorry to hear you had/have to spend so much time on this. “Smart” isn´t exactly what I´d call this if it´s obviously sped up, though.
I´d say contact CS if you know for sure it was sped up (would be really a shame if they did that regularly to new sellers), but then again probably your buyer would say they got it like that and you can´t prove otherwise, so that probably would only lead to CS telling you to check the file when you get the order and to work it out with your customer or cancel it.
In case they try more “smart” stuff, like demanding of you to cancel after you delivered without telling you any reason or what they´d want you to revise (I got that from someone who ordered my transcription gig; their very obviously very fake profile was gone not long after that; I had paused my gig so they wouldn´t order again from that or another profile, such people usually have more than one account, and I was so miffed that I never unpaused it lol), I´d definitely tell CS the whole story. But I do hope all goes well, you can deliver and get paid and a great review - unless you don´t want to pour even more hours into this for much too little money and rather cut your losses and cancel either way.