Shopify ignoring selected collection template

[hookbeak]

I have 3 collection templates. The standard and two i have created.

I set a number of my collections to use one of my templates, on nearly all the collections this has worked fine.

However, some collections completely ignore whatever template i select and show the default. I can select any of the three and save it - in the dropdown it shows the correct template - but when i view the page it's showing the default template.

Any ideas?