Ordering in Default product sort ordering doesn't work

[K3N0Bi1]

Hello,

There seems to be an issue when I set products in Ordering sort on a site I'm working on. I've searched the web and several forums only to find out that Ordering option along with others does not work properly. For example, when I visit the first product of some categories there is a previous button (that should not be there) that redirects me to another random product of the same category. Same goes for next button.
Why does this happen and how do I fix it? Am I doing something wrong or is this a bug or something?

Thanks in advance!

Currently using:
Joomla! 2.5.27 Stable version
VirtueMart 2.6.12.2 version