Why in Safari (iOS) after adding a class to an element, styles are applied only after scrolling?

Question

css

There is an adaptive page , on the mobile version the left catalog with filters is placed in a moving fixed block. In this block, each filter element is made into a span with the class "filter-item". In JS, on clicking on such an element, the "checked" class is added, which has a different background and color. In Chrome, it works as it should, in Safari on the iPhone 5s, by clicking on the element, the class is added, but the styles are not applied. But as soon as you scroll at least a pixel in any direction, everything works out, the span is repainted.
What could be the problem, why Safari draws such a delay? ..