I've been having random problems with bluetooth.  I have a 5000 and an iphone 5s.  It will work great for a stretch then it will just suddenely drop the connection.  I can be looking at the deivice list on my phone and when i try to reconnect, it will for about 2 seconds then drop again.  If i'm on the phone it doesn't drop the call, just changes back to the iphone.  I've tried reseting my phone, and forgetting and redoing the BT connection.  

Any suggestions? Thanks

Try this:

First I would power cycle the phone. Turn it off and on again and see if that helps. 

Next I would try:

press: HOME BUTTON > SETTINGS (gear icon) > RESTORE SETTINGS > BLUETOOTH SETTINGS> RESTORE. 

This will restore your bluetooth settings on the head unit to factory.

After completing that process I would power cylce the phone again, once it starts up go into bluetooth settings (settings icon > bluetooth) on your phone and tap the little i in the circle to get to the settings for the bluetooth device and select "forget this device" and then pair again. 

You should send an email to pioneer support as well. they are pretty helpful and your unit could be defective. :/

Thanks