How did you update to version 19.4?
Did you:
- Automatically update (while online)?
- Install the standalone 19.4 file on top of the old version?
- Do a clean install?
How you updated will dictate recommended actions.
You shouldn't see the main avast window pop-up whenever you download a file unless you invoke windows explorer scanning.
Well, in a way you were invoking an avast windows explorer scan via IDM after
every download, but not in the way one would think.
It's not necessary to invoke a windows explorer scan scan everytime you download a file or picture. You can remove the IDM virus scanning line without any issues whatsoever. If you kept your settings the way they were, what you were complaining about would never resolve.
Avast automatically scans all files when opened, created, or written in real-time and does so silently unless it detects something is wrong. This real-time scanning includes online web activity. You will see a pop-up window alerting you to a block or suspicious activity.
Pay attention when these occur.
Remove the IDM setting and extra step created by IDM, and you won't have further issues. IDM is not necessary to alert
IF a virus is found. IDM doesn't alert. IDM can't alert as it is not an anti-malware program.
Reboot and trust avast to do what it is supposed to do.
https://en.wikipedia.org/wiki/Antivirus_software#Real-time_protection