The update should honor existing settings but sometimes it doesn’t which is usually a bug, however it should certainly not add components which were not previously installed.

I’ve updated three machines varying from Avast Free to Internet Security and the PUP detections were still enabled after the upgrade while no additional components were installed. I do see a scenario here though. Did you enable “Scan for PUPs” in General > Settings or was it done individually for each shield?

The Sensitivity setting changing to default is most likely a bug but I’d need more proof before I can escalate that. Majority of people use the default normal sensitivity so I’ll need to wait for the next version to test that unless someone else hasn’t updated and wants to test.

Regarding the search engine changing to Yahoo, that is the browser cleanup component. In order to remove “bad” add-ons, it changes the search engine. I’m personally against this but that won’t change. Best advice is not to install the browser component module.

There was an issue with scheduled scans which has been fixed in the latest version 17.8.