No, unfortunately this problem still occurs after the slave AP was reset.  It only joind the master AP on one occasion.  A definitive resolution would be great.  There's probably a bug in the firmware version, but I can't download firmware images.

So I finally got the 2802I AP to join the controller in the other 2802I with stock firmware, unfortunately it's still a bit of mistery what is happening inside those APs and why they act this way, seems those are bugs.  All I did was: connect the PoE...

I'm having this exact problem on the AP2808I-E-K9.  There's nothing at the "debugging" level in the logs when the DSINTF-GET-FAILED message occurs.  The Cisco troubleshooting guide also says nothing useful about this error.