BBCode not rendered in base model

[makaleks]

When base model (not abstract) contains BBCodeTextField and the child model is saved, the _rendered field is not saved in the database. In general, even the pre_save signal is not raised for base model, when child is saved. Nevertheless when base model pre_save and post_save signals are raised by child model pre_save and post_save receivers, the situation is not changed. The SQL prompt shows that raw and rendered are different, while print(), placed at the end of process_bbcodes(), shows the rendered content normally at pre_save - but doesn`t save.