While I still hope that there would be a fix in the future verisons that would allow to remove such stuck files…
…here is how I managed to remove a stuck file from the Virus Chest in the similar situation
(on Windows 7 64-bit SP1):
1. Find a file “index.xml” here
C:\ProgramData\Avast Software\Avast\chest
(If you don’t have visible extensions enabled in your Windows, you can verify it’s an xml file by right clicking on it and looking into its propreties).
If there’s no such file in that location, try to search for the “chest” folder on your system drive, until you find it.
I recommend enabling showing of hidden files in your Folder properties (you can google search how to do it on your OS).
2. Temporarily disable the self-defense of Avast
(Go into Settings > Troubleshooting and then uncheck the “Enable Self-Defense” option, and confirm).
(Don’t forget to re-enable the self-defense after you have finished following this guide!)
Also, disable the Behavior Shield (you can re-enable it, if you wish, after you have finished following this guide).
Also, you might want to add into Exceptions the path of your falsely detected file (you can type it in manually if necessary), if you still have the file and wish to keep it.
Make sure to fully close the user interface’s window of Avast now.
3. Just in case, make a copy of that file “index.xml” into any other location as a backup, so you can restore it if necessary.
4. Now, open the original file “index.xml” (in its original location)
with a Notepad or any other simple text editor.
You’ll see one or more entries there, in this fashion (XML structure):
https://i.imgur.com/bjxEz6L.png
Using the values in blocks “OrigFileName” and “OrigFolder” you can identify your stuck file
(or it could be just one such entry there, if you don’t have any other files in your Virus Chest).
For that stuck file,
you only need to change that long string of numbers and letters inside the block called “IDPBlob”.
(Don’t try to modify the name itself of that block!
And Don’t try to change anything else in that file, or it might make things worse.)
Modify a couple of randomly chosen characters in that value (letters or numbers) into some other numbers or English letters.
All that matters, is that the original value there was changed.
Then save these changes in that “index.xml” file.
5. Go to Avast’s Virus Chest now, and try to delete / remove that stuck file, by selecting it (checking it) and using the bottom button to access the option to remove it. (Don’t use the dropdown menu or button on the file entry field itself).
In my case, it worked!
6.
You can re-enable the self-defense of Avast now in settings > Troubleshooting!
And, if you still wish to continue using the Behavior Shield, you can turn it on again as well.
I discovered this solution after multiple tries and errors, experimentally.
Some other ways I tried also seemingly removed the file, but it re-appeared whenever a new file would end up in a chest.
My final solution described above permanently removed a stuck file though.
If the solution above didn’t have any effect,
do the same thing again, but also do the following operations (while the self-defense of Avast is disabled):
1. Remove everything from your Virus Chest, so that only that single stuck file is left there.
2. Enable showing the hidden files in your OS (google search how to do it).
3. On EACH hard drive or SSD you have, in their root, locate the folder named “$AV_ASW”, which is hidden by default.
Inside all such located folders find folders named “$VAULT” and inside those find files named “vault.db”
Remove those files from all those folders.
Basically, make sure all those folders have no files in them.
4. Try to remove the stuck file from the Virus Chest again.