In my case I use the greek characters and when I try to add an item to the cart I get logged out. When I try to add another item with latin characters I don't get logged out, but everything works perfectly. I read already too many solutions but all seem to have the same result. The solutions that I have found where to change the $product_name_rules into the following:
Either: '\d\D'
Or: '[:print:]'
or anything similar. I tried all of these but none seem to be working. But when I use for example the '[:print:]' statement I don't get logged out but the item isn't added also to the cart, although I get the message that a new item added to the cart.
If anyone could help me I would appreciate it.
Thank you.