David Beazley on Nostr: I realize this is kind of geeky, but I'm always interested in "failure modes" of ...

I realize this is kind of geeky, but I'm always interested in "failure modes" of things. So, what would cause a persistent perfectly circular black spot in the middle of what looks to be a perfectly good display? (This has been here for weeks on a local gas pump. It's always there regardless of what's being shown).