Comment 4 for bug 1969315

This problem happens with transmission-gtk package. A workaround is to use transmission-qt package instead of transmission-gtk.

With transmission-gtk, when you open the torrent's properties panel, apart from scramble the texts, buttons, etc, there are GTK related errors spammed every few milliseconds (can be seen with journalctl). This is an example of these errors:

may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkLabel'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_label_get_text: assertion 'GTK_IS_LABEL (label)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_label_set_text: assertion 'GTK_IS_LABEL (label)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkTreeModel'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_tree_model_iter_nth_child: assertion 'GTK_IS_TREE_MODEL (tree_model)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_tree_model_iter_nth_child: assertion 'GTK_IS_TREE_MODEL (tree_model)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_widget_set_visible: assertion 'GTK_IS_WIDGET (widget)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkToggleButton'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_toggle_button_get_active: assertion 'GTK_IS_TOGGLE_BUTTON (toggle_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_block: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_toggle_button_set_active: assertion 'GTK_IS_TOGGLE_BUTTON (toggle_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_unblock: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkToggleButton'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_toggle_button_get_active: assertion 'GTK_IS_TOGGLE_BUTTON (toggle_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkSpinButton'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_spin_button_get_value_as_int: assertion 'GTK_IS_SPIN_BUTTON (spin_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_block: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_spin_button_set_value: assertion 'GTK_IS_SPIN_BUTTON (spin_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_unblock: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkToggleButton'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_toggle_button_get_active: assertion 'GTK_IS_TOGGLE_BUTTON (toggle_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkSpinButton'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_spin_button_get_value_as_int: assertion 'GTK_IS_SPIN_BUTTON (spin_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_block: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_spin_button_set_value: assertion 'GTK_IS_SPIN_BUTTON (spin_button)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_unblock: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_block: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkComboBox'
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_combo_box_get_model: assertion 'GTK_IS_COMBO_BOX (combo_box)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_combo_box_get_active_iter: assertion 'GTK_IS_COMBO_BOX (combo_box)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: gtk_tree_model_iter_nth_child: assertion 'GTK_IS_TREE_MODEL (tree_model)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_unblock: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: instance with invalid (NULL) class pointer
may 01 07:17:38 fpgrpi transmission-gt[9098]: g_signal_handler_block: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
may 01 07:17:38 fpgrpi transmission-gt[9098]: invalid unclassed pointer in cast to 'GtkComboBox'