How specifically are you locking with group policy? If using software restriction policy, I thought there was a default rule to already allow C:\Windows and C:\Program Files so you wouldn't need to specify every single Avast exe. Applocker might be similar but I have no real experience with it.
In fact, if Avast changed it's list of exe's during an automatic upgrade, you would have to keep modifying your policy. Specifying Avast's individual exe's sounds like it could be the wrong approach and you might need to review your lockdown rules; you might be too restrictive
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