Not able to decode FLEX-A and FLEX-C messages

[stevenmcastano]

As requested I'm opening a new issue for FLEX decoding. I've got an RTL-SDR v4 running in multiple different SDR software packages... this one was while running SDR++. PDW is decoding it fine, but multimon-ng is not. I tried piping the network stream from SDR++ into netcat listening on UDP port, as well as just sending this file through. I've tried the following command lines:

nc -l -u 127.0.0.1 2001 | pv | ./multimon-ng -t raw -a FLEX -a FLEX_NEXT -f auto -u -

As well as trying to send it through sox first:

 sox -t wav ./audio_sample_single_message.wav -esigned-integer -b16 -r 22050 -t raw - | ./multimon-ng

Link to the audio file:
https://drive.google.com/file/d/1E_pONRB7IxE0qwHLYAmiF2Yd-i8B6G3E/view?usp=sharing

Here is the decode from PDW: (redacted the phone number)

0025833   16:45:12 25-07-24 FLEX-A  ALPHA  6400  Fr:SMS:7********5
                                                 I am at parents house [22]