Hello there, @rnd 
Thank you for your patience! I have a few more steps for you to try with the client you are working with.
First, please encourage your client to clear their cache again. Additionally, please ask them to try the same action from a different wifi network to confirm is they encounter the same situation or not.
Second, please ask your client to get their x-nf-request-id. Here is a resource from our Support Guides on how they can do this! We will use this to check our data logging system and find some specifics about this request.
Lastly, would it be possible for you to share a screenshot of what the client is experiencing and a screenshot of what expected experience should be? Comparing these two images will give us further information about the situation.
Thank you!