Some drivers believe the Monaco layout was tweaked without their knowledge ahead of the 2019 race.
Officially, the circuit remained at precisely 3.337 kilometres from 2018 to 2019.
But some drivers disagree, and according to Auto Motor und Sport raised the issue at the driver briefing.
They claim the second part of the swimming pool section is now tighter than it was.
"Last year, I could go through flat. Now I had to gently lift at the exit," said Racing Point driver Sergio Perez.
