Whoever happens to have downloaded either of the two first official nightly builds for macOS Monterey (https://avidemux.org/nightly/osx_monterey/) following upgrade of the bundled FFmpeg from 4.4.2 to 5.1.2, i. e. from Feb 9 or Feb 12 (2023-02-09 or 2023-02-12), please update to a build from Feb 27 (2023-02-27) or later, as it contains a fix for an enormous memory leak present in the two earlier nightlies.