So far, no. I have reset search index, reindexed and tried the PowerShell commands from the KB article. Search in Windows Explorer works just fine - only Start menu doesn’t. Troubleshooter says incorrect permissions for search directories but I haven’t fiddled with those. Tried repairing permissions and giving everyone permission but doesn’t help :-(

What worked for me was uninstalling the September cumulative update and the August cumulative update[1], then flagging those two to avoid that they get reinstalled the next time Windows updates[2].

[1] https://www.windowscentral.com/how-fix-start-menu-and-search...

[2] https://support.microsoft.com/en-us/help/3183922/how-to-temp...

The first time Windows update created the spike in CPU, the "fix" was to restore the cache used by Cortana at "%USERPROFILE%\AppData\Local\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\LocalCache"

Come the 2nd update that borked the start menu, I suspected that it might be because I restored the cache and so the "fix" was not applying correctly. I then proceeded to wipe the cache altogether and it simply rebuilt itself.

Protip: If trying to delete files using windows built in tools throw up errors (mostly permissions related. this will not help you delete a file whose file handle is locked though.), trying using rm from cygwin. Works every single time.

An update that fixes the broken search functionality has been released, at least for me it worked and the search is again running normally.