When mob is spawned with mob egg on top of tripwire, dispenser fired arrow doesn't hit them when triggered by tripwire

When mob is spawned with mob egg on top of tripwire, dispenser fired arrow doesn't hit them when triggered by tripwire the mob was spawned on

What i expected to happen: mob would spawn and trigger tripwire,firing the dispenser a few ticks after the mob touched the tripwire,damaging the mob.
What happened:the tripwire seemed to fire before the mob touched the tripwire, resulting in Zero damage
To reproduce:
1. Make tripwire, hooked up to a dispenser with arrows
2. Spawn mob in front of dispenser on tripwire.