I have two fake PS3 controllers. I have been able to get one working fine. Is there anything specific to get a second one working via bluetooth? This question by Chris Barr has some good information; RetroPie & PS3 Controller over Bluetooth . Unfortunately, he does not clarify if he got two to work using bluetooth at the same time.
I am using the latest Retropie. Nothing added except the controller drivers.
There is nothing special needed. Just patience and some voodoo.
The problem apparently fixed itself.