I dunno. Maybe like 1 in 5. Possibly more than that. It seems to happen most often on notifications where I click it right after the notification comes in. 

 If you wait e.g. one minute after receiving the notification before tapping on it, would you expect it to be blank? 

 I wouldn’t ever expect it to be blank. It just happened again. I recorded a video this time. https://v.nostr.build/In9NWxHNCW4EqJuS.mp4