And if this happened, what solution can be used to fix?
Pull in the changes from Bitcoin Core. Sync a new node with that software. Once it reaches the invalid block, it will reject it. From there, start mining a fork. Once that has more work than the original blockchain with the invalid block, that will become that coin's blockchain.
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Thanks.
start mining a fork.
-> How to do this?
and then how deal already happened transactions after invalid block?
so this means coin split as different (like ethereum and ethereum classic?) and people should switch to new forked coin?
Then what happen people's existing balance? existing balance also become back to forked time?