My cart count / mini-cart doesn’t update, is that a bug you fix?

Yes, that’s the WooCommerce cart fragments AJAX failing. The ?wc-ajax=get_refreshed_fragments request returns a 403 or stale nonce, usually because a page-cache plugin (or a CDN like Cloudflare) is caching the cart fragment or the nonce. We fix the cache exclusion, the nonce mismatch, or disable fragments where they hurt performance, so the quantity and totals refresh instantly again.