it depends on the relays you're connected to; I've noticed that some relays are polling on others so sometimes a zap that was posted on a relay you're not connected to won't show up, but later it's pushed so it appears later

I started fetching zaps from other relays and aggregating them on my relay to make this better; if you know where your zaps are being sent to lmk and I'll connect to those by default / fetch from them