Update 9/3/18: Below is the statement BleepingComputer received from Malwarebyes concerning this topic:
“Upon first discovering the conflict between Malwarebytes and Avast, Malwarebytes reached out to a product manager at Avast, who put us in contact with one of their Real Site feature developers. This developer initially indicated that there was a problem with Malwarebytes Web Protection driver implementation. After cooperation and receiving detailed analysis from our lead driver developer, Avast determined there was a flaw in their driver implementation. They have indicated they have a fix and plan to release an update, but they did not provide any timing. In the meantime any Malwarebytes users experiencing these issues are advised to disable Avast’s Real Site feature.”