Scotland head coach Gregor Townsend questioned Zander Fagerson’s red card and a last-minute penalty call as his side were edged out by Wales.
Fagerson was sent off on 53 minutes for an illegal clearout on Wyn Jones, with Scotland 17-15 ahead.
Jones barged over three minutes later, with two tries from Louis Rees-Zammit and one from Liam Williams earning Wales a 25-24 win.
“I’m more just questioning the process,” Townsend told BBC Scotland.
“It took a long while to see a replay [of the red card]. We saw slow motion, one angle and then there was another delay in getting more decisions.
“These are important parts of the game. Obviously if he did touch the head – I thought initially he got under and clear of the head – but if he did touch the head, then it starts at red and you mitigate down because of the late movement.
“That’s what the TMO was hinting to the referee [Matt Carley] but the referee made the decisions and you have to abide with it and deal with it.”
World Rugby, Law 9: Foul Play
20. Dangerous play in a ruck or maul.
a. A player must not charge into a ruck or maul. Charging includes any contact made without binding onto another player in the ruck or maul.
b. A player must not make contact with an opponent above the line of the shoulders.
Scotland threatened to snatch a late victory when Duhan van der Merwe broke down the right touchline in overtime at Murrayfield, but Owen Watkin’s terrific tap tackle halted the Scotland wing.
Townsend felt his side should have been awarded a penalty at the resulting ruck.
“I’m convinced we won a penalty on that right-hand side there,” he said. “Chris Harris was on the ball for about five seconds before he got told to get off it.
“Sometimes these things don’t go your way and you need to be ahead on the scoreboard in the last two minutes and not behind.”
Tries from Darcy Graham and Stuart Hogg had Scotland 17-3 up in the first-half, with an opportunity to kick for goal to extend their lead to 17 points.
In the end, Wales defended stoutly before adding a try of their own before the break, and Scotland’s Gary Graham had a score disallowed shortly after the interval before Wales responded through Williams.
Townsend backed his players’ decision not to go for goal, but rued wasted chances and some ill-discipline.
He added: “Not scoring the try when we were on the line – that would have helped things then the red card made it tough.
“Our discipline let us down today, and not just the red card. Penalties in the first and second-half. That’s the difference really between getting a very good performance to a Championship-contending performance.
“I firmly believe in this team and with the confidence they have in the way in they’re playing they can be a match for anybody, in any stadium.
“We know we’ve got a big opportunity over in Paris but I would back the players to bounce back after today.”