Avast file scanner ignores infected files by default. The default settings for the file scanner is “repair if possible else ignore the file”. Unlikely most time the repair fails and then the file is ignored. I had this problem several times. The file was always infected and had to be removed so I had to delete the file after the scan manually.
I think it would be much safer if avast would move the file to chest by default.(if infected and not repairable)
It is not unlikely at all that a repair is not possible.
In the beginning there where only viruses.
They where a little piece of code that attached itself to the end of a file.
Therefore it was pretty easy to remove the infection and restore the file to its original condition.
Nowadays there are a lot of types of malware, not just viruses.
They work different and that makes it very likely a file can not be repaired.
That means avast is exactly working like it should with the settings you have selected.
The default action - “Fix automatically” - is not the same as “Repair”.
“Fix” actually means “Try to repair, if it fails, move the file to Chest, if even that fails, delete the file”. So that default settings actually tries every possible action avast! knows (before leaving the file as it is).
I believe more information would be needed - name and location of the file, the result shown in the popup, possibly the result from FileSystem Shield log… etc.