When I try to export a frame from the timeline I'm working on, sometimes, premiere will export the frame from the attached proxy instead of the full resolution media.
The normal behavior in premiere seems to be that the frame export always exports the frame from the full resolution media as long as it is available. Recently, I have run into a problem where it will export the frame from the proxy media insted. I can tell since I encode my proxies with a proxy logo overlay so it is easy to know which I'm working with. This happens randomly reguardless of wether the proxy media is toggled on or off. In order to get the frame to export from the full resolution media again, I have to quit premiere and sometimes even restart my computer. Both full resolution media and proxy media are online and viewable within premiere when this happens. I wouldn't worry about it since restarting solves the problem but since I have to export frames 5-10 times per timeline, it gets annoying really quick.
I am on a macbook pro running OS version 10.15.6 with Premiere Pro 14.4.0. All media is on an external thunderbolt 3 drive.
Exact same issue here. Haven't found a work around to get the full frame exported - other than unlinking the proxy media. It's like at that point Premiere HAS to give me the full res frame. Re-starting is a pain as my project file is massive (500mb+) and connects to 30TB of 4K footage - so it takes forever to save, quit, re-start.