graphic blocks

dopo l'ultima build ho una frazione di secondo blocchi grafici, molto fastidiosi e che rendono difficile l'esecuzione, l'ho disinstallato e reinstallato, ma il problema rimane, ho bisogno di un consiglio, grazie

 

What are graphic blocks? Perhaps put a screenshot to show them?

 

while I ride on the track, everything freezes for a few tenths of a second I can't take a screenshot

 

try during a replay.
Is it anything like this? the white blocks flashed so quickly, I couldn't even tell if they were square while driving. But on replay I could stop at the exact frame.
https://forum.studio-397.com/index.php?threads/alfa-romeo-33-tt-12-1975.66079/page-6#post-1110732