Here's what I can report, a day after re-install (and this is a second re-install, after a first one about 2/3 weeks ago)
Re-install was done using the Avast Clear - only once, in spite of advice to un-install all former versions ? I don't know if there any priors left, always updated thru the interface.
First was a bit of a surprise yesterday, the interface looked like old one - at least not the latest i remembered. Under settings / update, I could update the virus database but not the application update: the option was there of course, but clicking it did not trigger anything. Today, back to the current interface, as much I can tell and application update option operating, there is no need for any update. I have gone thru Smart Scan, Full Scan, Boot Scan and a Malwarebytes scan as well, no results: all clear.
Only I am back where I stood 2/3 weeks ago: AvastSvc.exe regularly clogging things up for a few mn (85% to 95% of CPU, more or less 600,000 K of memory - as per Task Manager and Process Manager which I run to check on things). Also, I am in hot country and not too much aircon, so I run Speedfan: temperatures are 2 to 3 deg. C higher than usual.
Event viewer still lists a loop of Avast Update Helper / Avast Browser Update Helper attempts that fail, and repeat, and fail and so on. Trying for Event Log Online Help leads to a Microsoft blank page: not too helpful.
So, I guess it would not bring much to try and re-install again? As well, I guess it would be a pain in the neck to try and go deeper into details, without high chances of finding out what's wrong? Never had that since about 2005, as much as I can remember) but then things change (laptop getting old, Windows 7 support soon ending).
A question I'd like to ask: is it reasonably safe to connect to the net without Avast on the comp, thru hotspot on a mobile phone that does run Avast also (free version) ? Usually connecting to emails, newspapers, financial sites and Youtube: all very classic, never really had alerts except maybe when streaming some series or movies (which I could limit to Linux laptop then).
Thanks for any advice
Sergei