On D10.4.1, Can not set values on immutable configuration

I've just encountered this issue on the new formal release of the 3.x branch too. No difference using either the DEV or current formal release. Using latest D11.1 core

image_widget_crop.links.menu.yml and the routing at image_widget_crop.routing.yml seems ok, so can only assume it's an issue with the settings form /src/Form/CropWidgetForm.php

The error seem to be with the submitForm() function

If $this->settings is replaced with $this->config('image_widget_crop.settings') the settings save correctly and the error is gone.

Sorry - should have rolled the MR against DEV, but the patch will apply to both branches

Sorry - should have spotted this 🐛 Can't save image widget crop settings in Drupal 11 Active