# Prefetch Frames not working?

In Blender 2.92, I have Prefetch Frames enabled in the Video Sequence Editor, and a Memory Cache Limit of 16384 in the Video Sequencer > Memory Cache System settings. I've closed and reopened Blender and rebooted, but still don't see an orange stripe in the sequencer indicating that frames are being prefetched (and I do get some performance/framerate issues during playback).

Is there any reason prefetch would be working but not displaying the orange indicator stripe? Do I have to enable that in the display? Based on the performance issues it would seem that prefetch is just not working...

Edit: I should also say that I am splicing mp4's together that I recorded from my camera. It's a fairly simple setup...