X3 pin 4 has a "less than 90 degrees angle"
I made a T out of it.
Name your vias GND so it connects both top and bottom copper layers
I already fixed that, see last my attachment picture.
Why not use pads instead of vias to connect your wires?
Could you explain more please as I am unexperienced. I use the vias for their holes to put headers in them so that i can attach my shield on top of arduino.
I think your pads are too close to the edge. DRC didn't like it.
Why doesnt drc like my library part consisting of vias, but likes plain vias at the same position with the same size? I could just place a Via same size same distance next to my existing header-vias and it would give me no error.