Sometimes hosting companies use very aggressive caching, which is causing necessary session data to be cached and not updated properly. In order to fix that you need to add all of your customer account related pages to a list of excluded from caching and also if possible add the following session names in the “exclude from caching” list in your hosting caching setup:

coupon_code, timezone_name, menu_layout_style, selected_location_id, agent_id, customer_id