Has anyone used Digital Output 6, and has it presented any difficulties?
I’m working on a project with 2 Xbees using I/O line passing on DIO0-7. The transmitter detects changes on DI0-7 and passes them to DO0-7 on the receiver. Pins 0-5 and 7 work perfectly, but pin 6 doesn’t respond. Setting the pins manually on the receiver via AT commands (ATD04 or ATD65 for example) gives similar results: DO0-5 and DO7 respond as expected, but DO6 remains fiercely independent 
All the pins are configured identically (DO low). By setting 6 to DO high and writing that to non-volatile memory, I can sometimes get DO6 to be high on power up. Sometimes it will go low after a second or two, sometimes it’ll stay high till an ATD64 command (but a subsequent ATD65 command won’t take it high again).
I’ve tried three different XBee 802.15.4 adapters, with firmware versions 1xCD and 1xE6. I have them on the v1.1 XBee adapter boards from Adafruit. I’ve checked the solder joints and swapped the Xbees from one board to another, but no matter what I’ve done, DO6 has remained unresponsive. In all other respects the XBees and adapter boards work perfectly: they communicate with one another, pass I/O lines (except for 6!), XCTU can read and write their settings, upload firmware, etc.
All the pull-up resistors are enabled (the default setting), but turning them off doesn’t change the issue with DO6.
I’d appreciate any insight, or at least if someone could confirm that DO6 works or doesn’t work on their XBee.
Thanks!