OKX recently announced that they had been experimenting with a collection program, but have now halted the test. Unfortunately, the incident has had widespread effects on the network, with more than 330,000 transactions currently stuck.
Bitcoin network congestion tends to increase during times of high transaction volume or significant events in the crypto market. For example, during the 2017 Bitcoin rally to $20,000, the number of unconfirmed transactions in the mempool reached around 180,000, resulting in delays of several days for users waiting for their transactions to be processed.