Weird Smart Scan behaviour - very worried

Running AIS 2015 on Win 8.1 with all relevant updates and service packs.

Here’s the issue: I set Smart Scan to run, went off to make breakfast, came back approx ten minutes later and found that the Quick Scan window had been opened. I clicked back to Smart Scan from the side-bar, and Smart Scan resumed at about 52% completion. Smart Scan then finished and reported no problems.

I haven’t had time to do a full scan yet. Is this behaviour by Smart Scan normal? Should I be worried?

Does anyone have any idea about this? I’ve never known Avast to randomly stop a scan or switch to another window without user intervention before.

Is there some sort of program log that I can pull up that would let me know whether anything is wrong? If it helps, I think that the description of the Quick Scan window that interrupted the smart scan was slightly different than normal. It included a phrase like “this is part of Smart Scan”.

This and another unusual incident has been concerned that my system may have been fundamentally compromised.

the Quick Scan window had been opened.
It is a known issue that the scan windows opens after a scan is finished. Very likely it will be fixed with the next program update.