Random audio glitches followed by level dip after rendering video in Nuendo 13

After rendering a videofile with only a 3 stereo audiotracks soundtrack, my client noticed 2 audio glitches/peaks followed by a short level dip in the file.This was a project I also rendered video in in Nuendo 12. Never had any problem after video-rendering. I went back into the project to check the timestaps, but there is no problem in the project itself. Then I chose to mixdown audio only and put it together with video in Resolve. No problem. It looks like something went wrong during rendering in Nuendo. What could this be?