This is warning about a UI focus bug when fast-traveling between Flame Altars rapidly.
Here’s what happens: you port to Altar A, then immediately port to Altar B and open the deactivate prompt. The game's "active altar" focus hasn't updated yet; it’s still pointing at Altar A. So when you confirm deactivation, you destroy Altar A, not Altar B. Your base goes with it.
The fix is simple: before deactivating any altar, check the name displayed in the UI. If you’ve named your altars (which is why naming matters), you can confirm you’re looking at the right one before you pull the trigger. If the name doesn’t match where you physically are, wait a bit or re-interact with the altar before deactivating.
Short version: the rapid port causes a selection desync. The name check is your sanity check against it.