Philip, just out of curiosity do you have all the exclusions in place between MBAM Pro and avast - avast in the trusted list of MBAM and MBAM in the file shield exclusions of avast.
There are also four malwarebytes exe files to be placed in the avast BhS trusted processes ( mbam,exe, mbamservice.exe, mbamscheduler.exe, mbamgui.exe ) I found that since the latest MBAM and avast update that several people have been having unusual problems till all these exclusions were put in place.