Villa held by West Ham after VAR drama
Australian referee Jarred Gillett and VAR official Tony Harrington spent over five minutes debating whether West Ham defender Konstantinos Mavropanos' effort hit the arm of Tomas Soucek on its way into the net.
The replays were inconclusive, with a post obscuring the view of a sea of arms and legs on the goal-line.
But Mavropanos' goal was eventually ruled out, one of three chalked off for the Hammers, to spare Villa from a damaging defeat.
Nicolo Zaniolo had equalised for Villa after Michail Antonio headed West Ham into a first-half lead.
"We've had four handballs this week that didn't go for us. It's what VAR do, it's their decision not ours, we can't do anything about it. It's there to do the job," West Ham boss David Moyes said.
"In the second half, Villa stepped it up, they were the better team for periods. But I was really pleased with how we performed overall."
Villa manager Unai Emery added: "The referee decided it was handball. We didn't control the game in the first half.
"We changed tactics in the second half and got chances to score a goal. In the end we did score. We have to accept it."
Fourth-placed Villa are now three points clear of fifth-placed Tottenham in the race to qualify for next season's Champions League via a top-four finish.
But it was a frustrating afternoon for Emery's men, who have played a game more than Tottenham and had hoped to take advantage of the north Londoners' loss at Fulham on Saturday.
West Ham made a strong start and Lucas Paqueta had a shot deflected wide by Soucek from Jarrod Bowen's cutback, before Vladimir Coufal's drive was blocked by Emiliano Martinez.
The breakthrough came after 29 minutes when Coufal swung in another cross and the diving Antonio got in front of Ezri Konsa to nod in his first goal since August.
Kudus had the ball in the net shortly afterwards, but Gillett had already blown for a foul on Martinez by Antonio.
West Ham had another goal disallowed, more contentiously, just after the break when Antonio bundled in a Bowen corner.
Martinez totally missed the ball, but VAR ruled Antonio had touched it with his arm.
Villa began to rally as West Ham's energy levels dipped, and Alphonse Areola saved a 20-yarder from Youri Tielemans.
An equaliser looked inevitable, and it came in the 79th minute when Tielemans sent Moussa Diaby scampering down the right.
Diaby's cutback found fellow substitute Zaniolo, who arrived in the box right on cue to prod the ball past Areola.
In stoppage time, Matty Cash stopped what looked a certain goal for James Ward-Prowse before Mavropanos scooped the ball into the net from the resulting corner.
Bowen and Soucek forced the ball over the line, but Gillett was eventually beckoned to the pitchside monitor and decided it was handball against Soucek.