Client Error

Everytime I play Mutation Mode I usually get client error.Why does it only happen when I play Mutation Mode. What is Client error. How do I fix it. I also heard you can get client error if you continuesly use the knife for the AK-47 Knife. Please help me I dont want to lose connection on the last round of Mutation Mode when I play all 16 rounds. It happens a lot in research facility where the glass is. Tell me if this also happens to you. Does it get annoying to you. Are you lucky to not get the client error. Please comment and help me. Thanks