Symfony Warning: filemtime(): stat failed

it's an update form, if i try to update the first time it works but the second time i got this error:

Warning: filemtime(): stat failed for project-path/vendor/ocramius/proxy-manager/src/ProxyManager/GeneratorStrategy/EvaluatingGeneratorStrategy.php(54) : eval()'d code

and the exception is catched here:

 $form->handleRequest($request);

What i understood that's liated to cache, so i cleared it. But i got always the same problem : it works just the first time after i got the same error.

What's the solution please? thank's