Tarkin's Blunder

A decision Tarkin made toward the end of the Battle of Scarif, may have lead to the destruction of Death Star. When he arrived at the battle, on board the Death Star, he immediately orders the destruction of base on Scarif, instead of destroying the Rebels lead ship, which had just received the transmission of the plans. Now obviously he didn't know that the plans had been sent, but keep in mind the Captain on the Star Destroyer that Vader was on did know, and Vader immediately knew what had been sent. Rather than trying to recover the stolen plans, why not just destroy them, along with a Rebel command ship. Then after the super weapon recharges, you can destroy Scarif.

But regardless, destroying the base on Scarif was a mistake. In the process of doing so, you destroy one of the two copies of the Death Star plans, and the only one you were in possession of. Just in case you are unable to recover the stolen plans, you could just have your engineers review the plans, and figure out what the weakness is, and find a way to protect it.