Product navigation is stuck, repeating same products

[iWim]

Hello,

I have two webshops where the product navigation stops working properly.
This happens where products have the same name.

When products have the same name the navigation will start navigating between two of them.

How it should work:
Product 1 > < Product 2 > < Product 3 > < Product 3 > < Product 4

What it does:
Product 1 > < Product 2 > < Product 3 > < Product 3 > < Product 3 > < Product 3 > < Product 3 > < Product 3 > etc., etc.

Here's where you can see this in action:
4 products, 2 with the same name. When you click on the first product and then use the arrows to navigate to the third product, the navigation is stuck between the third and fourth product.
https://moedermelk-sieraden.nl/oorsieraden

Is there a way to fix this? A setting, a small change in the code?
Or is changing the names the only solution?

Thank you.
Wim

[iWim]

Er... bump? 

[GJC Web Design]

if products have the same name and you have SEF one assumes the alias url is identical?

have u tested changing the names?
tried with SEF off ?
etc etc