Quick answer: Unreal Niagara systems not ticking when game is in picture-in-picture mode on mobile? PiP suspends some tick groups - explicit Always-On flag on critical effects.
Mobile player puts game in PiP; combat continues; VFX freeze. Looks broken.
Mark VFX Always-On
Effect Type > Always Active. Niagara ticks regardless of PiP.
Or pause game in PiP
Auto-pause when not in foreground. Avoids the visual mismatch.
Audit PiP mode
Each subsystem (VFX, audio, AI): PiP behavior. Document; consistent.
“PiP is a foreground-state change. Subsystems opt in to background ticking.”
If your game supports PiP, the per-subsystem behavior is design work. Plan it.