Hi Dexmix,
Welcome to the forums. This thread is a little dated and your question sort of belongs in an updated FAQ. For now, let me redirect you to this thread.
The short version:
Renoise plays XRNS files. It’s not a MOD/XM/IT player. Compatibility with other formats is known to be imperfect. The feature is only there to help you get started in case you need to rework songs into XRNS.
If you are looking accurate MOD/XM playability, you should try Milkytracker. IT, try Schism Tracker?
Regards,