Controversy ensued at the Santiago Bernabeu as Paris Saint-Germain were denied a penalty and Thibaut Courtois was saved from a red card by VAR intervention.
Courtois brought down Mauro Icardi as he rounded the keeper and the referee initially pointed for a free-kick on the edge of the box, sending off the former Chelsea goalkeeper.
But he checked with VAR whether or not the foul occurred inside the box, which would have seen the visitors awarded a penalty but the red card overturned due to the double jeopardy rule.
Yet the referee went over to consult the pitchside monitor, instead being alerted to an incident involving Marcelo way back on the halfway line in the build-up.
Gana was penalised for an innocuous foul as he was judged to have pushed Marcelo, cancelling out the incident which looked set to give Paris Saint-Germain a lifeline in the form of either a penalty or one-man advantage.
The French side were trailing 1-0 at the time after Karim Benzema's strike.
They went in behind at the break after being denied a chance to equalise by the VAR intervention.
And fans slammed the chaotic and confusing scenes as further proof of the technology having a negative impact on the game.
One viewer even branded it the "most controversial decision in the history of VAR so far" with others stating "VAR will kill football".
PSG are no strangers to VAR controversy in the Champions League.
They were left furious by a late penalty given for handball against Presnel Kimpembe last year, which allowed Manchester United to complete a dramatic comeback to dump them out of the competition in the last 16.
