Hiya,
I am sorry to hear you are having trouble with your blender.
I have added a link below for a help video on removing the coupler and also added a link below for the spanner we recommend purchasing to help remove the old coupler:
https://www.youtube.com/watch?v=nhnuaSCoVjQ
https://secure.kaparts.co.uk/sku/CouplerSpanner
I hope this helps :-)
KAParts
KAParts, March 2020