Timing is everything (to Calibre). It take little to flip to the Not Working side.
To be less susceptible to those changes, you would need to freeze all aspects of the connection. Obviously you can't (and should not) forgo updates to security and OS Patches.
Add in the Covid 19 effects on Network Traffic, and I am really surprised that the Internet has been as stable as it has.
So, IMHO, Luck has been with you till now
