411 error WordPress MU + WooCommerce

We have been developing an e-commerce version of our product, Run Your Own Website. We have two live sites, one about to go live and one in production. However, we have hit a problem.
If you are logged in as the client into the dashboard and you attempt to filter the product list, it crashes with a 411 error in Chrome. In Firefox it just hangs.
This is the case even if the client account is an administrator. The only way to fix it is if the user is make a super admin.
I have had this issue previously on another MU setup, a client was unable to paste in javascript in a post even though they had admin access. I do not know if it is related but I do not know how to resolve it.

I would be very grateful for any suggestions. Please see the attached screenshots. It is the same user, one taken when he was also a super admin and one where he was not. Thank you very much.

Best wishes

Clive