Yep, I've tried to do arbitrage on one exchange during dumps (there's quite a lovely way to realize there will be a massive dump done on the exchange) and most of my trades couldn't even execute because the trading engine can't meet the demand.

When you look at the price history (and open orders history) between some pairs on one exchange you'll find that during these spikes there was no arbitrage being done at all.

One example is seeing the price on ETH-BTC pair being constant despite BTC dropping 10-20%, and then combing back in 5-10 minutes.

The elevated chance of an exchange going down in the middle of a crisis is actually a major source of the risk that one needs to take into account when evaluating the expected profitability of arbitrage strategies.