Video Playback Problems in Reaper

[tallone]

Hi. I'm having some problems playing back video in Reaper. The video in question works fine outside Reaper. I import it. It plays fine from the start, but if I ever navigate to a section by clicking in the timeline somewhere, the video starts to be glitchy. It appears that the frame rate is significantly reduced or something. If I go back to the beginning (using the transport button) the video is fine again, until I click somewhere in the timeline. I've tried switching decoder priorities and watched the video tutorials but I cannot for the life of me figure out why I'm having this problem. Any pointers would be appreciated. REAPER v6.12c/x64 rev 8af23c (June 15 2020). Windows 10 x64. 4 GB RAM, Intel Core 2 Duo 2.26 GHz. The video is 1920x1080 25 FPS MPEG. FWIW, the video imports and plays back correctly in a couple other video editor programs I have.

Thank you.