Why is there a 2 minute egg spawning atop the gym I took?

I see wierd spawn glitches like that from time to time

Sometimes, when you have your game open for a while and then put your phone in Standby with Go still active, and later on turn it on again, it doesn‘t seem to load things properly. I had the same thing just now. Suddenly an egg appeared on a gym nearby with like 45 minutes left until hatch. At least for me it is like that. Sometimes, when an egg hatches during Standby with active Go, it doesn‘t even show the raid boss until I click on the gym.