The largest network Bitcoin had a stale chain of length two yesterday, which the research arm of cryptocurrency derivatives exchange BitMEX referred to as “quite a rare event.”
It was at height 656477 that multiple blocks were produced. Here, as new blocks are mined that refer to one of these blocks as their parent, the one with the heaviest chain survives while the other blocks become stale.
“This was not a consensus issue (all blocks were valid),” noted BitMEX Research.
If a transaction occurs in one branch and a conflicting one occurs in the other branch, then it is either an RBF fee increase or an actual double spend. Despite the chain split, no double-spends were detected in this case.
Also, it is not as rare an event; the frequency of such occurrences is actually fairly common.
“Consensus forks of length 1 are as common as one per week. There's nothing particularly notable about a temporary fork of length 2. It's a normal part of the protocol. The frequency at which this will occur is the equation by Satoshi in the white paper,” said Bitcoin advocate Andreas Antonopoulos.