Janome my style 16 bobbin thread knotting up

Question

While sewing on the trusty my style 16(not the overlocker) the bobbin is jumping up and down in its casing making a banging noise while sewing and the bobbin thread is knotting up underneath the clothing.
i have oiled the bobbin casing and made sure all the screws on the plate are tight and it didnt help at all,
please help