Floating Ouput Comissioning Button Xbee-Pro and Short Range

Hi at all,

I’ve got a problem with my XBee modules. I tested many different modules with the Pro Featureset(ZB), short/long Range, Chip-, RPSMA and U.FL antenna.
In my project I’m using the Commissioning button to detect the signalstrength in the network. I flashed all modules with the same X-CTU configuration.
Some of the XBee’s deliver a constant voltage at DIO0 (3,3V). When I pull down this pin to gnd they send the Node ID Identicator and when I take off this connection the voltage is 3,3V immediately.
The problem is three of my XBees did not deliver the constant voltage. Everytime they are not in Sleep Mode the voltage at the Pin is nearly zero even though the connection to ground is take off. Not before they go to Sleep again (after 30 seconds) the voltage is 3,3V.
Does anyone know this problem? What is my misstake?
The internal pullup resistor is enabled, however the same configuration works on other modules.

Mysterious is that one short range Xbee with chip antenna works and the other doesn’t. The other non-working module’s are long range S2 modules with u.Fl connector. First I thought the S2 is the problem, because my other long range XBee’s are the S2B Version. But one of my short range XBee’s work and they are the same.

If you need any more information, please ask. Sorry for my english, I hope you understand my problem