Whatsapp Notifications Delay

Hi, i bought iphone 16 plus in mid of november. The problem i'm facing is the whatsapp notifications. the summarise notifications is not working for whatsapp only. when i receive the msg and my screen is on, i see 1-2-3 msgs on whatsapp icon but got the notifications after 10 seconds. moreover, when i'm texting someone and chat is open during texting i only see single tick on my msgs and when i close my chat then double tick appears.

all other apps are working fine. only whatsapp creating this issue. i have reinstalled it, updated it did everything but problem remains same.