Earlier this week, an irrevocably fork occurred in the test network Segwit2x, as a result of which the creation of new blocks stopped for almost 20 hours.
The proposal scalability of bitcoin Segwit2x has taken at a closed meeting of a number of industry representatives in may of this year. The protocol provides for the activation of Segregated Witness with the support of 80% of the miners hash and the subsequent hardfork, that increase the block size to 2Mb.
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https://bit.news/eng/in-the-testnet-segwit2x-there-was-an-irrevocably-fork/