Hi,
I’ve tried to reproduce the issue in the way that I have installed an old version 39141, updated to 39902 and then to the current 39915 and wait for the updates. The updates seem to be working properly.
If the update has occured after an internal error message, it would indicate that the avast daemon (taking care of too many tasks including updates and currently being rewritten) has stucked from a certain reason.
Unfortunatelly, if this behavior repeates after an uninstallation and a clean installation, I don’t know what to advise at this moment.