XBee Flicker/Blink w/ Line Passing

I’ve seen this question posted a few times on the interwebs but i haven’t found a clear but answer. I’ve got line passing enabled on my series 1 xbee’s and all seems well and good except for a random “blinking” of an LED i have attached to one of the digital outs. I’ve confirmed the voltage dropping to 0 with a multimeter and with other leds. I’ve also tested the digital input pin on the OTHER XBee and it is a clean consistent 3.3v. At first i thought it would be dirty power but i tried a 9v w/ a 3.3v regulator as well as an arduino sourced 3.3v. I’ve also tried caps across the rails both before and after (and both) the 3.3v regulator. I’ve also tried playing w/ the XBee timeouts, retries, pooling time, changing it to line detection mode, changing the i/o’s, swapping the xbee’s, swapping batteries, swapping regulators, ensuring latest firmware, etc all w/ the same exact result… Huge sigh… Any thoughts? I’m totally /stumped.

Thanks for reading!

Update : did some sniffing in API mode and the blink/flicker seems to be accompanied by a modem status update packet (0x82) with a status of “watchdog timer reset”. i believe this is related to sleep options on the radios but i’ve got sleeping completely disabled on both.

the mystery continues!