PD injector switch time deviation

[Dimitri16V]

I checked block 23 today and it seems like the #4 injector is lazy
It switches very slowly from while the rest of them change values rapidly

any ideas what would cause that ? am I looking at a defective injector ?
No CELs
348K miles on original injectors

 

[Dimitri16V]

compression on all cylinders ranges from 420-450 psi

Cyl4 tappet has some wear but i dont see how that what affect the injector duty cycle