We have received the report from users who saw MovieRecorder crashing when using the remote control feature with Catalina or Big Sur. The crash only concerns the "Server" (the MovieRecorder being controlled by another one), and does not happen on the "Client" (the MovieRecorder controlling another one).
We have identified the issue. It happens in a code that hasn't changed since a while, and does not happen with previous versions of the OS, so it's an issue specific to macOS Catalina or later. If possible, you can revert to macOS Mojave to fix the issue.
If you can't, or don't want to, we are working on a new version of MovieRecorder (version 4.4) which uses a different (new) method for the remote control. And it is working well in our tests. And we have a pre-release version available for you.
We advise all users with macOS Catalina or Big Sur and using the remote control feature of MovieRecorder to test that version. As usual, make sure to run extensive tests with the pre-release version to make sure that it works in your specific use.
Even though we are not responsible for the issue introduced in macOS, we try to offer the best experience to our users, whatever the reason of the issue may be. Thus, we'll continue to work on this and provide a release version as soon as we can.