What puts a slash in the path

[vistad]

I have an HTML structure

<a href="{{ .Params.categories | relLangURL }}{{ .File.BaseFileName | relLangURL | urlize }}">

that creates a page link of a type:

category/productPage.html like e.g. cars/volvo.html

The problem is, it does not always put a slash between a category and a product page.
For some pages it puts a slash between them and for others it does not - and I don’t see why.
May be someone can hint where to search for a solution.
Thank you

[vistad]

I’ve found and fixed my problem: the problem was the colon characters, contained in timestamps that are part of filenames. As soon as I removed colons - everything worked fine!