Well I agree there shouldn't be any inconsistency, but the question is what is turning the windows firewall on (after avast had previously switched it off). Is there a possibility that this other program is enabling the windows firewall again.
Even if it is this other program enabling it again, I would question why it requires the windows firewall on for your wifi to work, that is strange. Unfortunately not using the avast firewall I can't really offer any advice in that regard (possibly trying different setting, Public, Work, Home).