EUR/CHF trades at 1.4897 and is not expected to move much until after the 15:00 options expiry as there is a large option rolling off at 1.4900 at that time. Close to expiry, options are either entirely in the money or out of the money, so both the buyer and the seller of the option have an exposure one minute and no exposure the next. That’s why when expiries are large, prices tend to gravitate toward the strike.