Reopen goerli/netstats-server#13 by @veox
Most commonly visible on bar-graphs for block time, difficulty, transaction count...
The most common cause is someone accidentally connecting a node from network X to dashboard of network Y; but this could also happen due to malice.
In general, the dashboard is overly trusting in accepting the data fed to it as correct, and does not gracefully handle conflicts.
Reopen goerli/netstats-server#13 by @veox