Problem demuxing a selectable subtitle from avi (no ogm)

[GM_Wildfire]

I'm having a problem with several .avi files that have selectable subtitle files and only one audio stream.
The files play perfectly with Windows Media Player(6.4.09.1121) and load the subtitle file in DirectVobSub(2.23).
I can choose if I want to view the file with or without subtitles just like any .ogm file or files with a separate
.ssa/.srt file.

But when I want to demux the text file with VirtualDubMod(1.5.10.1),
it doesn't appear to have a text stream, only an audio stream.
There must be a text stream somewhere because DirectVobSub sees one...
How can I demux the subtitle file from this avi?

I've used dafreak's How to Convert OGM to DVD Guide https://www.videohelp.com/forum/viewtopic.php?t=222005
with a little tweaking to create VCD & SVCD from .ogm files with hardcoded subtitles successfully, but this method doesn't work with this avi file unfortunately.

When I load the file into VirtualDubMod, I get this message;
| VBR audio stream detected
| VirtualDub has detected an improper VBR audio encoding in the source AVI file (audio stream 1).
| The current preference is to rewrite the audio header with standard CBR values during processing for
| better compatibility. This may introduce up to 826 ms of skew from the video stream. If this is
| unacceptable, decompress the *entire* audio stream to an uncompressed WAV file and recompress with
| a constant bitrate encoder. (bitrate: 136.8 +- 20.1 kbps)
| Do you still want to rewrite the header?
| YES/NO

I always choose YES to that
(the audio stays in sync with the video when I frameserve it to TMPGEnc(2.57.41.146-Plus)
It doesn't execute the "Parsing OGG media file", but loads immediately.
Under Streams -> Stream List [Available Streams] There's only the audio stream listed, no text stream
There are no comments and no chapters


Under Streams -> Report:

Input files :

---== Video stream ==---
Source : [Input AVI file]
Description : AVI video stream
Length : 00:20:41.781

---== Other stream ==---
Source : [Input AVI file]
Description : AVI audio stream 1 [tag 0x0055, MPEG-1 Layer 3 (MP3)]
Length : 00:20:41.784


DirectVobSub has selected the following files to display the subtitle stream:
V Show Subtitles
V Subtitle 1

Gspot info from the avi file:
Size: 233 MB (or 238,947 KB or 244,682,740 bytes)
Type: OpenDML AVI, "rec list" style
IMRR: 1.16
I/L: 2113 ms (50.7 v.frames) Split: No

Video Codec
4CC: 02tx/xvid
Name: XviD
Runtime: 00:20:42 (29,773 fr)
x:y: 640x480 (1.33:1) [=4:3]
Bitrate: 1439 kb/s
FPS: 23.976
Qf: 0.195 bits/pixel

Audio Codec:
Name: 0x0055(MP3) ID'd as MPEG-1 Layer 3
Bitrate: 137 kb/s (68/ch, stereo) VBR LAME3.92
Fs: 48000 Hz

[GM_Wildfire]

Could anyone please help me with this problem?
I've been trying to find a solution for it for months.