I would try taping another show with a fresh battery in the A3 module.
Also, the OKMIIR mics can take *a lot* of sound, so you might want to try plugging the mics directly into the Line In on the iriver, and see how that works at a show... because the Line Input on the iriver puts out around 3V of plug-in power.
I suggest trying out only the plug-in power because it works fine for some mics (e.g. Sennheiser MKE-40s took A LOT of bass, and did not distort, using only the plug-in power on my iriver). Since the OKMIIRs can also take high SPLs, they should perform pretty well with plug-in power.