Never mind, I found the option. For future reference, you have to go to File System Shield, click expert options, then look in “Actions” and the second action it performs by default (if it can’t sandbox) is deletion. Change that to “ask”. Fixed.
Feel free to delete this post/thread.
avast doesnt delete any file unless the move to chest action fails…
file system shield>>expert settings>>actions>>set primart action for a virus,PUP and Suspicious back to move to chest…
Sorry, I worked this out just as you were posting. I was frustrated because I saw that AutoSanbox was on and thought Avast had gone rogue and was deleting things anyway. Thanks for the reply 
does the file shield detect anything as suspicious?.. is that not the sandbox?
i have the same issue Avast delete encryption file fro my usb key all the time (and there are not in the ‘Virus Chest’) - must disactivate Avast to run the exe…
you are posting in a topic from 2012 
see instructions here >> https://forum.avast.com/index.php?topic=194892.0
scroll down to >> SPECIFIC INFECTIONS LOGS
Follow MCShield instructions and copy / paste the log here
This is a almost 5 years old dead thread.
If you want help, start your own thread and provide details please.