I found a thread where some people had similar problems and they seem to solve it with a patched version of bluez:
https://retropie.org.uk/forum/topic/42/shanwan-ps3-controller-pi3-retropie-3-6-bluetooth-setup/126
it seems that you need a forked version of bluez:
https://github.com/luetzel/bluez
more details on: https://luetzels.raspiblog.com/?p=1870
Maybe someone from the devs can fix the problem with this information?