How to "export the frame capture file"?

GPU Frame Capture has recently stopped working for me.
Currently, when I run it I get alert -

Unexpected Replayer Termination
Replayer terminated unexpectedly with error code 5. Please export the frame capture file then file a radar

When I'm in this state, how do I "export the frame capture file"?

"Export..." is greyed out under File menu.

I'm using Xcode 12.0.1 (12A7300) targeting Apple TV 4K running tvOS 14.0.1 (18J400).