The tip was very simple: i just turned off all audio in preferences while rendering the selected song:
Preferences,audio,select driver type: no audio, MME/DirectX, asio; just select no audio and render. It sounds perfect, no pops and glitches anymore.
Thanx for the tip - i hope it'll help some others with similar problems, if they missed that post. The one with this tip also wrote he used to do that in every host or program where it was possible, cause it almost always gave a better result.
I'm happy i read that