I followed your suggestion, and there were no zombies to be found. In the meantime, I found a temporary solution for the issue. The problem was that I wanted to export the FCP project using the main app as the action, but FCP was executing it, which caused the crash. To resolve this, I added an auxiliary application to the project to handle the export instead. This change has prevented the plugin from crashing. However, it will still crash if the user opens the app from Applications while it is already open in FCP. This behavior seems to be present in other plugins as well, even in simpler ones.

Here is the requested crash report. I was testing other workflow extensions and was able to replicate this issue with them. I even tried Frame.io and could replicate the issue there as well. To replicate the issue with Frame.io, follow these steps: Download Frame.io from the app store Open the Extension from Final Cut Pro (FCP). Without logging in, open the Frame.io app from your applications. The workflow extension should crash. Crash report