Track Matte Key Causing Source Video to Disappear

I've been dealing with this issue for some time, and I am using Windows 10 with Version 14.9.0 installed. I am not sure how reproducible this issue is, because sometimes my Track Matte Key works as expected, and other times it does not. I am using a PSD file as the source for my Track Matte Key, and have it located right above a nested video sequence that I want to have a cropped effect for. The PSD file only has a transparent layer and a white raster graphic on the second layer, which masks in the correct video cropping. Sometimes this crops correctly, but other times, like now, it does not work. My track matte key effect is set onto the nested video sequence (Video 2). Once I set the source on the track matte key to Video 3 where the PSD file is located, my Video 2 layer video disappears. None of the elements on the timeline actually disappear; it's just the video that disappears from the program view. I can also confirm that before I set the source on the Track Matte Key, I am able to see the PSD file image I place on there in its transparent and white form. If there's any other information and clarification I can provide, do ask because I am not sure how clear my description of this issue is. I would appreciate any thoughts on this. Thank you!