Bluetooth dongle and Zigbee/Conbee II together - not a good idea

I added ASUS Bluetooth BT-400 dongle to my system, with an extension cable. I also have Conbee II with an extension cable as well. They are about one meter from each other.
After that, the batteries of my Zigbee sensors began to run out much faster and the radio coverage of Conbee II was much smaller. The sensors began to disappear now and then. My hunch is now that BT-400 is causing disturbance to Zigbee radio frequences. Could this be the problem?
Is there a way to use a bluetooth dongle in this kind of a setup?
An addition: all sensors are now working right after I removed BT-400 from the system.

Move them 2 meters apart.

If a sensor is 10 meters away, then 1 meter change would be 6 degrees (if the sensor is at an orthogonal direction, but probably not). How would that make any difference?

I’m hypothesizing that the BT and ZigBee radios are interfering with each other.