I just updated Audacity from 3.7.8 to the 4.0.1+dfsg-2 version, and while
most changes in the interface are mostly-fine, the program is mostly
useless for me: It consistently crashes when saving a project's audio to an
MP3 file. I have the following log to the console:

21:58:52.824 | INFO  | main_thread     | ActionsDispatcher::doDispatch | try call action: export-audio
21:58:55.515 | WARN  | main_thread     | Qt              | qrc:/qt/qml/Muse/Interactive/FileDialog.qml:25:1: QML FileDialog: Window.window only supports types derived from Item

(audacity:3733903): Gdk-WARNING **: 21:59:06.053: Tried to unmap the parent of a popup
21:59:13.639 | INFO  | main_thread     | ActionsDispatcher::doDispatch | try call action: nav-next-panel
21:59:13.644 | INFO  | main_thread     | CommandDispatcher::dispatch | try call command query: command://navigation/next-panel
21:59:17.462 | INFO  | main_thread     | ActionsDispatcher::doDispatch | try call action: nav-next-panel
21:59:17.475 | INFO  | main_thread     | CommandDispatcher::dispatch | try call command query: command://navigation/next-panel
21:59:20.911 | WARN  | main_thread     | Qt              | qrc:/qt/qml/Muse/Interactive/FileDialog.qml:25:1: QML FileDialog: Window.window only supports types derived from Item
21:59:43.141 | INFO  | main_thread     | [AU3] LoadEncoderLibrary | Attempting to load LAME from system search paths
21:59:43.141 | INFO  | main_thread     | [AU3] InitLibraryExternal | Loading LAME from libmp3lame.so.0
21:59:43.141 | INFO  | main_thread     | [AU3] InitLibraryExternal | Actual LAME path /usr/lib/x86_64-linux-gnu/libmp3lame.so.0.0.0
21:59:43.141 | INFO  | main_thread     | [AU3] LoadEncoderLibrary | LAME library successfully loaded
21:59:56.758 | ERROR | main_thread     | Qt              | Object 0x557273045510 destroyed while one of its QML signal handlers is in progress.
Most likely the object was deleted synchronously (use QObject::deleteLater() instead), or the application is running a nested event loop.
This behavior is NOT supported!
qrc:/qml/Export/ExportDialog.qml:283: function() { [native code] }

[1]+  Aborted                    audacity /tmp/FV0015.MP3

The program does not _always_ crash, but it does happen frequently enough
to be quite upsetting.

Given the main role of this program is to process audio files,
I believe a frequent crash on audio file creation warrants the “important”
severity.