Blockchain Reorganizations Can Remove Confirmations Without Erasing Transactions

A crypto transfer can show confirmations and later appear pending if nodes switch to a different valid branch. That change affects which blocks make up the active chain; it does not rewrite a transaction inside a block that has been removed from that chain. Nodes may temporarily follow separate branches when blocks reach them at different times. They use the network’s rules to settle on a branch. Bitcoin (BTC) nodes compare the cumulative work of valid candidate chains, so the branch with more blocks does not necessarily win if another has more accumulated work.

Source: TokenPost