Subdomain Shows Elements of TLD- how?

[Fairyglass]

We have a retail website, with a trade website as a subdomain. To gain access to the trade website, customers must have an account. The trade website sells many of the items on the retail website, but not all, and in different quantities.
When some trade customers log in to their accounts on the trade website they see the left hand menu, products and pricing from the retail website. They are able to browse products on the retail site, but can't see the trade prices/products.
I can't recreate this- I can log in as the customer and see the proper trade pricing and information. I've checked on several machines, and with several browsers, but more than one customer has the problem so I'm unsure how best to check further. Is it likely to be a caching issue with their machines, or a settings issue on the site? Network settings are separate of course for the sites, and both pass network tests without issue.
Any help would be appreciated!
Retail site is www.fairygoodies.co.uk, wholesale subdomain is http://wholesale.fairygoodies.co.uk.

[Mike Hughes]

I can't think what the problem might be.

The best thing I can suggest is to ask the customer to send you a snapshot of the page they're on so you can see what url is being shown.

It might be that some link on the wholesale sight is referencing the retail site and usually a link checker program will be able to find it. This is unlikely to work if you need to be logged on, so another option might be to temporarily disable the logged in requirement and check the links across the site.

Mike

[Fairyglass]

Thanks Mike,
I've asked the most recent customer who's had a problem to send me a screenshot and will check that. I've looked into the links and can't find any, but will double check using a link checker. The sites were built at separate times, so I don't think there should be any common links, but it's certainly worth considering.
Best wishes,
Ben