ffmpeg or mplex DVD mpg or vob file with m2v and wav or lpcm

Question

I would like to burn my favorite audios to a DVD with menus and hard links to vob files from the XTRA directory on the DVD. So I will have DVD-Video and MPEG files with artist names on the same DVD. I create VOB files for authoring and do hard links in ISO. But have trouble.

ffmpeg.exe -fflags +genpts -threads 4 -i %FNAME%.m2v -i %FNAME%.wav -f dvd -c:v:0 copy -bufsize:v:0 1835008 -b:a 192000 -ar 48000 -c:a:0 pcm_s16be -map 0:V -map 1:a -map -0:s %FNAME%.vob

Through much errors:

[dvd @ 000001d0a3e81840] packet too large, ignoring buffer limits to mux it
[dvd @ 000001d0a3e81840] buffer underflow st=0 bufi=12134 size=79437
[dvd @ 000001d0a3e81840] buffer underflow st=0 bufi=14158 size=79437
...
[dvd @ 000001d0a3e81840] packet too large, ignoring buffer limits to mux it
[dvd @ 000001d0a3e81840] buffer underflow st=1 bufi=3876 size=4096
[dvd @ 000001d0a3e81840] buffer underflow st=1 bufi=3808 size=4096

So I used another case, which I don't fully understand either.

ffmpeg.exe -threads 4 -i %FNAME%.m2v -i %FNAME%.wav -f mpeg2video -c:v:0 copy -bufsize:v:0 1835008 -map 0:v:0 %FNAME%-.m2v -f s16be -b:a 192000 -ar 48000 -c:a:0 pcm_s16be -map 1:a:0 %FNAME%.lpcm
DEL %FNAME%-.m2v
mplex -f 8 -S 0 -M -V  -o %FNAME%.vob %FNAME%.m2v %FNAME%.lpcm

Can you explain why the latter case doesn't have errors; why is the same file %FNAME%.m2v twice with a different name?

PS

>ffprobe %FNAME%.m2v
...
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, progressive), 720x576 [SAR 1:1 DAR 5:4], 25 fps, 25 tbr, 1200k tbn
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 49152 vbv_delay: N/A

>ffprobe %FNAME%.wav
...
Input #0, wav, from '%FNAME%.wav':
  Duration: 00:02:31.19, bitrate: 1536 kb/s
  Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, 2 channels, s16, 1536 kb/s

>ffprobe %FNAME%.vob
...
**[mpeg @ 000001d823a80400] start time for stream 0 is not set in estimate_timings_from_pts**
Input #0, mpeg, from '%FNAME%.vob':
  Duration: 00:00:26.48, start: 0.500000, bitrate: 2168 kb/s
  Stream #0:0[0x1bf]: Data: dvd_nav_packet
  Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, progressive), 720x576 [SAR 1:1 DAR 5:4], 25 fps, 25 tbr, 90k tbn
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 49152 vbv_delay: N/A
  Stream #0:2[0xa0]: Audio: pcm_dvd, 48000 Hz, stereo, s16, 1536 kb/s
**Unsupported codec with id 98312 for input stream 0**