system
3
maybe the BSOD isn’t caused because of AVAST?
one of the main reasons for BSOD are over-heating, usually when you put too much presure on your system, and the cooling-system is stuck from dust,
it may occure.
try to take a vacume cleaner and gentley clean the dust just to make sure 
another thing, what other av/firewalls do you have installed on your machine with avast currently to now?
another cause for bsod caused by higher-performence which is required from the system, is the motherboard.
try to check it as well, this was my problem before a lot of years.
that’s all what is coming through my mind right now, try the dust thing.