Read only mode error in edit site page of Manage Customers

When a read-only user having access to manage customers, they query a customer and choose a site to look into the details of the customer. After the work is done, the user clicks on cancel and the system throws the FND read only mode error message instead of going back to the manage customers screen.

This does not happen when the user goes to edit transactions, edit invoices, edit receipts or even in manage suppliers.

What could be the reason for this issue?