Seems strange considering you said the Apache web server used port 80, but you removed monitoring on port 8081. But you also mention SB, is this the Apache web server ?

I just wonder if it wouldn’t have been better to exclude the Apache web server executable in the the AvastUI, Settings > Active Protection > Web Shield - click the sprocket icon (settings) and scroll down to the Processes to exclude:

This way you leave port 8081 in the list of monitored ports as this is a common http proxy port and may leave you at risk from other functions using port 8081.