I thought I'd get an alert every time a watched thread was updated, but that doesn't happen.
Great tip on the watched threads tab! You can also use that view in the browser and I see build threads that were updated today, yet there is no alert anywhere when do a "Show All" on my Alerts and scroll back
EDIT: The Watched Threads seems to be the ticket!
Had this issue too, noted here:
https://www.reef2reef.com/threads/reasons-one-would-not-get-an-alert.357393/
Watched Threads was the answer to "resetting" them.