The Chest in Avast contains files suspected being insecure.
In addition it contains a copy or more of important systemfiles.
I have 4 of them. I would guess the problem is with checking/copying
your systemfiles to the chest.
But this doesn’t help you much, so we have to wait for the Avast gurus here…
Until then you have to live with the messages in your Eventlog, or try a fresh uninstall/reinstall of Avast.