Custom post type trouble

Hi,

got myself a custom post type (boilers). Made it like this:
[Code moderated as per the Forum Rules. Please use the pastebin]

On my central boiler page I have these custom posts for each boiler I’m presenting. Now when I go to the single post page (the actual post, because on central boiler page I just have link + excerpt) my breadcrumbs are not correct. Instead of giving Home > boilers & buffers > boiler_x. They give me Home > boilers > boiler_x. Where the ‘boiler’ link brings me to a whole new page which sums op te posts. Know what I want to achieve is just to go back to my boilers & buffers page when in single post view.

BTW I’m using the Breadcrumb NavXT plugin + workin local so can’t give you guys a live demo.

Can someone help me out please? Thanks in advance!