Wales coach Wayne Pivac believes referee Matt Carley was wrong not to award his side a key second-half penalty try in the 27-23 defeat by France.
France's Paul Willemse knocked on a try-scoring pass from Ken Owens to Josh Adams but the officials deemed the offence accidental and awarded a scrum.
"We have had a look at the slap down and I think the officials may have got that one wrong," said Pivac.
"That killed momentum as well."
Wales trailed 27-16 at the time and a penalty try would have reduced the deficit to four points. Carley decided to stick with the on-field decision by his assistant Karl Dickson after watching television replays.
Pivac was also disappointed with the award of a scrum penalty to France in the second half when he felt the visitors' set-piece had scrummaged illegally.
It was a controversial issue raised before the game, Wales prop Wyn Jones claiming France would "chase and cheat" at the scrum.
"Another disappointing moment was when the French tight-head [Demba Bamba] came on and went straight across the scrum and was rewarded for that," added Pivac.
"Those were the big moments in the game. The scrums, from our point of view, had gone OK up until that point.
"You have got to go with the forward motion but he clearly went across the scrum."
Pivac also admitted there was a key moment when France led 17-16 and man of the match Romain Ntamack intercepted a Nick Tompkins pass and sprinted away to score.
"If we convert one or two more we are truly in games and winning," said Pivac. "You come back to the intercept, three versus one. It was a 14-point swing.
"If we are accurate with our passing we probably score at the other end. That was a big momentum shift.
"We're frustrated with a couple of decisions we made ourselves after creating opportunities on one or two occasions.
"But I thought Nick played very well and was then pushed out to the wing. He did well there, he was involved in that last play.
"He bounced back well from Dublin."
Pivac gave France credit as Fabien Galthie's side claimed their first win in Cardiff since 2010 and remain on course for a Grand Slam.
"The French played very well and we have to take that loss on the chin," said Pivac.
Pivac also confirmed George North failed a head injury assessment (HIA) after a heavy first-half collision, while fellow wing Josh Adams was forced off the field with an ankle problem.
"George will go through the normal protocols for an HIA, while we will have to check Josh in the next day or two to see how severe it is," added Pivac.
Wales next face England at Twickenham on 7 March having lost successive games against Ireland and France.