For some reason

CONSTRAINT FK_stats_gsTbl FOREIGN KEY (gsId, Container)
        REFERENCES opencyto_preprocessing.gsTbl (gsId, Container)
        ON DELETE CASCADE

though it is part of the original schema definition. Could it be that I did not run the update properly? :(

I was able through pdAdmin to properly create this foreign key across schemas relationship and the cascaded delete worked!

Now I have to figure out why I had to do this 'by hand' and the original definition did not kick in...