I appreciate your kind offer. The real-world trial requires recompiling alsa route plugin - I have a pcm_route.c version for ubuntu 14.04 and 16.04. Many changes in alsa-lib in recent years, the patch must be rebased for each version to allow compilation of alsa-lib in the distribution version.
If you recorded 5 secs of clean closed-loop stereo data 1kHz -1dB gain 24/32bits generated by sox, for each card, I would do the analysis remotely offline just to test detection and recovery in my script and post the results here afterwards. It would be a great help, thanks.
Got sidetracked by Halloween here (700 kids in 3 hours. . .) I can get the recordings you asked for as wave files recorded in Windows. Most likely I'll use the reference files from RME as a source. They seem to be quite good and are open and available as downloads. Not sure yet which system to use for recording (Audacity, Reaper or maybe Virtins). Let me know if they will work. Otherwise I'll attempt to get the Ubuntu OS working (have not used it in this system for over a year. . . ) One key stumbling block may be the analog level in-out mismatch. At -1 dB it may not be consistent and potential for overload exists. We will find out hopefully tomorrow.