West Ham have agreed a deal worth £30m with Brentford for Benrahma and have been hoping to get the deal over the line today.
He underwent part of his medical yesterday and was expected to complete the checks ahead of signing the contract with the Hammers.
But it emerged that the winger failed the medical with West Ham and the deal could be in jeopardy with hours left in the transfer window.
There are suggestions that some issues could have cropped up during the checks, but Benrahma is still confident of becoming a West Ham player in the next few hours.
But it has been claimed that Brentford are unsure about the claims emanating from West Ham about issues around the 25-year-old winger.
The Bees signed the Algerian in 2018 and he made 94 appearances for Brentford over the last two years at the club.
He has rarely missed a game for Brentford in one of the most unrelenting leagues in the shape of the Championship.
It remains to be seen whether West Ham manage to get the deal over the line to sign Benrahma in the coming hours.