Data sometimes doesn't make sense

Sometimes, there are mismatches in the middle of the chain.
And sometimes, things look really strange - like here:


Why are `11269419`, among others, shown at all??

A couple of things that can cause problems:

- When the remote node in reality is a set of nodes, and we get round-robinned across them - and some of them are behind / still syncing / out of consensus with the others,
- When our local 'cache' of what a certain node has at block `X` goes stale, due to a minor reorg, but we never refetch `X`, and never detect that it was reorged.

No file, test, or entry point is named. Begin by tracing the node-monitor data path for the reported mismatches, round-robin node disagreement, and stale block-X cache; done means explaining and correcting why values such as 11269419 appear and covering both listed causes.

Written by the indexing model from the issue text.