(English is a little easier for me)
I am running into the exact same problem (I think so at least).
The raspberry Pi 3 run fine without the PXFmini.
However, as soon as I am adding the PXFmini on top, it tries to reboot but fail after ~4 seconds and keeps on rebooting and failing afterward. I have noticed that the PXFmini get fairly hot quickly.
Side note: When I power the raspberry Pi and then add the PXFmini on top there is no green or blue LED lighting on the PXFmini (for the short period it's trying to reboot). When I power the PXFmini first then the green and blue LED are on but the Raspberry Pi red LED is off.
Long story short, where could I find documentation about the interactions between the Raspberry Pi 3 and the PXFmini?
PS: As I was writing this, I just realized that I had plug the PXFmini backward on the RPI3... trying again tonight.