On an iPhone 14, I’ve had this come up regularly. There are two reasons that I think are causing it.

1. The vertical touch interaction is blocked or disabled temporarily. The solution that works for me is to swipe an item left or right to either reset or re-enable scrolling and touch gestures. Then the vertical scrolling will work again.

2. The feed load time - when the swiping left or right fix doesn’t work, it generally seems like it’s because the page is waiting to load and update additional items. I can see this happening more often when I’m on a slow network connection and then on fast Wi-Fi it’s just a slight pause and the feed loads.