Okay, here is what i done:
I flashed the current 5.20 beta (5.20-dev 2019/01/10 06:31) on a fresh USB-drive witch Etcher and uncommented #nvidia-driver=true, because in my test-system i have a nvidia GTX 750 Ti GPU.
Then i booted my test-system with the USB-Drive and connected my PS3-Controller via USB-cable for about 10 seconds, then disconnected the USB-cable and turned on the Controller.
After Controller was paired via Bluetooth i started Kodi. Controls in Kodi worked fine and i switched the Audio Output in Kodi, System Settings to the appropirate device (in my case it was "HDA NVidia, BNQ BenQ XL2720T on HDMI #1"), then started the addon FilmOn and watched a few seconds BBC live TV, to test the Audio Output (which worked fine).
Then i exited Kodi and went to ES Main Menu, Sound Settings, Output Device and set it to HDMI1. A jingle sound appered (this is, what i always do on first usage of a fresh installed image, because this way i can enable the Audio Output).
Then the interesting part began:
I connected a second PS3 Controller via USB-Cable for 10 seconds, disconnected the cable and turned on the Controller to pair it via Bluetooth.
After it was connected (now 2 Controllers are connected via Bluetooth) i started Kodi again.
Now controls in Kodi with the Controllers is messed up.
I pressed D-Pad right, and the Exit-Window of Kodi appeared. Then i pressed D-Pad down, which caused, that "Exit" was chosen, so that Kodi closed.
So we know at least two buttons, that are mapped wrong in this scenario. D-Pad right acts like the "PS-Button" and D-Pad down acts like B-Button (X-Button on the PS3-Controller)
When i'm back in ES and i disconnect the second Controller by turning it off (hold PS-Button for 15-20 seconds), and then start Kodi again, the controls work fine again.
Very strange behaviour.
Here the support file and the file, that i found in /userdata/addon_data/peripheral.joystick/resources/buttonmaps/xml/linux: