Add only one audio track but two track play same time

[Gokhan Kocyigit]

I use MP4 video file with AAC audio track. in Audio/Seleck Track menu I remove AAC track and add MP3 audio file. File has only one audio track. Video Output and Audio Output are Copy Mode and Output format : MP4v2 Muxer. Save file. I play the saved file (MPC-HC) in Properties window show two audio track. And I hear two audio track at the same taime. But (MPC-HC) Audio Track Menu show only one audio track.
For repair saved file : I use YAMB 2.0. Open saved file with YAMB. YAMB show one video track and ONE audio track. Save file with YAMB. New file is correct. I thing avidemux  is making a mistake.

[Jan Gruuthuse]

I cannot reproduce this issue? Please state your used windows, 32- or 64-bit, and avidemux version
Avidemux files:
- mp4 with mp3 mono audio track: VideoMonoMP3trackMP4.mp4 / 3.9 MB
- mp4v2 with mp3 mono audio track: VideoMonoMP3trackMP4V2.mp4 / 3.9 MB

Test files:
- test mono mp3 track: AudioMono.mp3 / 166.7 kB
- test video stereo aac track: Mp4v2withAacAudioP.mp4 / 4.1 MB

Be sure your mp3 track used is mono? play in VLC, Menu Tools -> Codec Information

[Jan Gruuthuse]

With loaded aac stereo track video.
- set Output Format to [MP4 Muxer] or [MP4v2 Muxer]
- Menu -> Audio -> Select Track ->
-- click on [Track 0 from video (AAC,Stereo, 128kbps)] (attachment AacStereo)
-- select in dropdown [.... Add audio track] and browse to AudioMono.mp3
-- select this mono mp3 track and click open. (attachment ReplacedTrack.png)
-- click [OK], Audio Tracks Configuration closes
- only save video now, do nothing else

that should be it

[Gokhan Kocyigit]

I use Avidemux 2.6.12 on Win7 64bit. I try same files and same actions today. This time there was no problem in files. I setup Avidemux 2.6.12 yesterday. And no restart windows. Maybe restart windows can be solved the problem. I don't know.
Thank you for your interest.
Yours sincerely