As I don't use manual update for VPS I can't comment, it would be interesting to know why you choose that option.
Have been troubleshooting a disk thrashing/system freeze problem. Drivers had not been updated and some updates were marked critical --- this helped. Focused now on disabling/enabling Firefox add-ins not compatible with latest FF version. So far this looks like the end solution. Avast auto updates at inopportune times aggravate problem.
You can try the true manual update of downloading the full VPS database, not just initiating an Incremental VPS update from the user interface. https://www.avast.com/download-update. Ensure that you download the correct version for the avast you are using.
Will consider this if no other solution is found.
As far as I'm aware the VPS updates have to be set to Automatic (default) to get the streaming updates.
I showed an image of the defs folder in Reply #1 above, that shows what VPS and streaming updates you received.
Sorry, I missed the image, probably thought it was an icon or similar. In C: \Program Files \AVAST Software \Avast \defs is one folder 16120100 where all the files within it are dated 12/1/2016 7:55 PM. So it appears AVAST has not updated since. It sounds like the solution you are advocating is go with Automatic updates with Streaming enabled.
The question remains what happened Dec 1 that altered an update system that was working fine and now precludes using certain update options?
Addendum: Same results as Pondus with suggested solution yesterday but willing to trust it's "OK"