Old Prof wrote:Statements about the need to verify the cache multiple times keep popping up here, so I've done that occasionally. In my experience, a second verification has
never turned up any files that need to be reloaded, so it seems to me that additional sequential verifications are a waste of time. It doesn't seem possible that my case would be unique in this regard.

My experience is the contrary: cache verify never succeeded on the first try.
I believe it is normal that our results differ because of the nature of the beast. The files are verified by comparing local information (often a hash of each file) to the corresponding information from a server, over the internet. If the request times out, or if there is any kind of network problem, some files will "fail to verify", even if they are not actually corrupted.
The internet being a fickle network, some will have more luck than others, depending on their connection to the Steam server.