Several users have reported problems accessing the forum with windows mobile phone. Win 8.1
The problem lies in the fact that they can not load the full page, or can load the page, but after that it does not respond to the touch.
The problem exists on the both skins (default IPS and Spectrum by IPSFocus). The problem appeared after the upgrade from 4.1.9 to 4.1.12.2. 
It seems that this problem does not exist in the latest version of Windows for mobile phones, ie. Win 10

Please check for yourself if you have a windows mobile phone:
https://www.fiat-lancia.org.rs/forum/

Is anyone else had this problem?

Try upgrading the phone to Win10 (If your phone is in the list that upgrade is available for)

I can confirm this. I just visited your site on a Nokia Lumia with Windows 8.1 and the page doesn't fully load. After refreshing the page, it freezes and becomes unresponsive.

It's strange because I tested my own forum and it loads.