Javafx - opening tab with another thread increase memory consumption - user-interface

Question

I am creating a new Tab in JavaFX with another thread everything works as expected besides the fact that when I click the close button to close the tab the instance itself not being killed. I can see the memory increases with every tab that I open and does not decrease when I close the tab.
Here is the code to create the tab:
Task<Parent> loadTask = new Task<>() {
#Override
protected Parent call() throws Exception {
FileXML xmlFile;
FXMLLoader fxmlLoader;
if (controller instanceof ProcedureController) {
fxmlLoader = new FXMLLoader(getClass().getResource("/fxmls/procedureTab.fxml"));
xmlFile = (FileXML) ActionsFactory.getActionsFactory().createAction(Procedure.type);
((Procedure) xmlFile).getExecutionProperties().setExecutionType(ExecutionType.NORMAL);
xmlFile.setFilePath(file.getAbsolutePath());
Platform.runLater(() -> setGraphic(initImageViewForButtonSize(PROCEDURE.IMAGE, 28)));
} else {
throw new UnsupportedOperationException("Controller Type is mismatch");
}
fxmlLoader.setController(controller);
tabController = controller;
setClosable(true);
Platform.runLater(() -> {
setText(file.getName());
getTabPane().setTabMinHeight(35);
getTabPane().setTabMaxHeight(35);
});
controller.getFileLoader().setFile(file);
controller.getFileLoader().set(xmlFile);
Parent parent = null;
try {
parent = fxmlLoader.load();
} catch (IOException e) {
logger.error(getStackTraces(e));
}
FileLoaderToolBar.setEditorController(editorController);
if (isNew) {
xmlFile.setAuthor(systemPreferences().getReporterPreferences().getName());
((AutoTesterFile<?>) xmlFile).setName(FilenameUtils.removeExtension(file.getName()));
xmlFile.save();
} else xmlFile.load();
if (controller instanceof ProcedureController){
xmlFile.setFilePath(file.getAbsolutePath());
}
controller.getFileLoader().setAndUpdateUI(xmlFile);
return parent;
}
};
loadTask.setOnFailed(event -> {
Throwable throwable = event.getSource().getException();
if (throwable == null)
new Alerts().raiseErrorAlert("Error", "Something went wrong :(", "Unknown issue occurred", false);
else {
Exception exception = new Exception(throwable);
new Alerts().raiseExceptionAlert(exception, exception.getMessage(), false);
}
});
loadTask.setOnSucceeded(event -> {
setContent(loadTask.getValue());
if (editorController == null) return;
if (!editorController.getEditorTabPane().isLastTabInPlace())
editorController.getEditorTabPane().getTabs().add(new AutoTesterTab(editorController));
});
Thread thread = new Thread(loadTask);
thread.setName("AutoTesterTabLoaderThread");
thread.start();