I've tested this with a DM/V1200BTEPEQ and a DM/V960A-4T1 against a D/240JCTT1-EW. Most of the testing has been done with only one call, but I've put up to four calls on there while testing.
I made a quick test program to illustrate the issue:
https://transfer.sh/%28/rdgj1/dm3_multiplay.wav,/10Yvv/jct.wav,/MZoQh/dm3.wav%29.zip
In the code being executed with dm3.wav and jct.wav, the software simply plays one prompt before waiting for a TDX_PLAY event to come back and starting playback with something else. With dm3_multiplay.wav, the board plays up to three prompts before returning the event, significantly reducing the pause between them.
