UE5 graphics issue after upgrading from 4.27 (VR project)

Hello!

We are in the process of upgrading our game from UE4.27 to UE5.4 for VR (Oculus, Pico, Steam). For some reason, we encountered a noticeable graphic issue in the current build that suggest a lot of flickering (white dots). So far, we could not identify the root cause of this and was hoping if anyone could give us some advice. I am attaching the relevant gifs for comparison.

Thank you!

My apologies for not knowing the correct terms to describe this, as I am a mere messenger (our Devs and Art teams are Korean)!
UE4
UE5