Seemed to be indeed an issue with the Controller, unplugging helped.
Made it to the Boss this Time, played closer attention to the Walls, might've been just a visual trick with all the deformation from the Bullets, the 'camera bending' and the slight transparency on the bottom infograph.
BulletPolygons don't stick to the ground tho, they can create some Airgaps for a while there.
Bossfight is a lot more Fun then the Level itself, I might be just too bad to jump properly, but it feels like more open Areas work better for this.