The video assistant referee is unable to reverse an offside decision that ruled out a West Brom goal because of the positioning of the camera.
Mbaye Diagne thought he had scored when he flicked Darnell Furlong’s shot into the net – but it was flagged offside.
Replays suggested it was Kyle Bartley who was offside, rather than Diagne.
However, the VAR could not determine whether Diagne was offside, so the on-field decision remained.
The incident happened with the game evenly poised at 0-0 but the Baggies made sure the early misfortune did not damage their survival bid as they ran out comfortable 3-0 winners.
The result – thanks to goals from Matheus Pereira, Matt Phillips and Callum Robinson – means Sam Allardyce’s side have recorded back-to-back league wins for the first time this season and are now eight points from safety with seven games remaining.
While Allardyce was pleased with the win, he was frustrated with the fact Diagne’s strike was ruled out.
“The big disappointment was the first goal that looked like a goal and should have been a goal,” he said. “I’ve seen all the lines and angles and I think they got that wrong. Gladly for us it hasn’t had an impact on the result but it could have done.
“You hope that when it comes up next time the goal is given.”
Speaking later in his post-match news conference, Allardyce was asked whether VAR is becoming a laughing stock.
“I’m afraid so,” he said. “Everybody can see it was onside. We have the angle. There are at least 16 cameras here.
“The reflection on VAR can be done at the end of the season and all parties should have an influential input into how VAR goes forward.
“That needs to be from the PFA [Professional Footballers’ Association], LMA [League Managers’ Association], Premier League and the FA [Football Association]. There are too many of us not being given an opportunity to express how to make it better.”
Southampton manager Ralph Hasenhuttl said: “Normally the offside decisions are the easiest – it is yes or no. Maybe they did not have enough cameras. I don’t know. It is easy to solve.”