There is so-called "pin risk," that could cause a larger loss than the "maximum". In this example, say the underlying closes at $102. The call you sold is ITM and is exercised, leaving you on the hook for 100 shares. However, the call you bought was OTM, so your broker won't exercise it for you, and you'd need to buy the shares at market to cover. However, you can't do that until the market opens on Monday. So if something happens that causes the stock to open substantially higher on Monday, you will be out whatever that difference is.

Many traders will close their positions before market close, leaving a relatively tiny amount on the table to avoid the risk.

That's a really good point. I'm pretty sure Robinhood exercises behind the scenes for you on the day of expiration 30-60 mins prior to close to avoid this.

I think the risk of that instance is low, since options are a legally enforceable contract. I think the brokerage has some liability to pay the contract then get the money from their client, but I don’t have my Series 7 so take me with a grain of salt.