When Sela is talking to Spock about the speech she's writing for him, the data pad to her right initially was a foot away then in the next shot is right next to her elbow.
Enterprise's sensors register the Vulcan ships travelling at Warp 1, meaning they were travelling at exactly the speed of light. It would've taken those ships decades, if not centuries to get out of the Neutral Zone, and much longer to get to Vulcan.
When Sela and her guards fire at the holographic images of Riker and his men, there is no damage to the wall behind them.
After the Vulcan ships are destroyed, Commander Riker asked Worf to keep him advised as soon at Picard and Data are safely on board the Klingon ship. Yet he makes no mention of Ambassador Spock. Given Spock's legend in the Federation, this seems odd. Even Picard was assuming Spock would be returning with them until he was informed to the contrary later.
As Data, Spock and Picard head to the underground tunnels to make their escape, a film crewman's reflection can be seen in the green crystal on the table.
It makes little sense, given they are still mid-mission on a highly-dangerous espionage venture, for Data to abandon his Romulan disguise while aboard the Klingon vessel. He would have no way of knowing if his disguise would be needed for further infiltration or excursion. It makes equally little sense for Picard and Data to return to the Romulan surface in their Starfleet uniforms, risking immediate discovery by hostile Romulans.
In the later seasons of Star Trek: Deep Space Nine (1993), Dominion leaders state that to hold a major world of the Federation, like Earth or Vulcan, would take "millions of troops and massive occupation armies". Yet, when the Romulans try to invade Vulcan, they use three small transports with around two thousand soldiers. This would be a pitifully small force and absolutely incapable of holding a major Federation world with billions of inhabitants. Even Picard notices this, and points out how the Romulan plan just doesn't make sense.