Vac error

When i play survivor every 2/3 games i get kicked off the game after the Vac says the game files have been modified or something like that. I never touched the game files and i just dowloaded the game from steam. This happens only when i play survivor and never when i play killer (it happened with 3 different survivors David, Meg and Claudette). I got kicked like this 4 times, can someone help me or explain how to not get this bug?

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