VORON 1.5: Bad first layer scaring

I made my first big print on my new VORON this weekend. After adjusting the level of the bed with my dial indicator I'am pretty happy with the general "flatness/adhesion" with my first layer.

Unfortunately i get really bad "scars" in the middle of the layer which makes strange patterns. Currently i have no idea whats wrong here.

Used settings

Nozzle: 0.6mm
Layer height: 0.4mm
Print speed: 60mm/sec
First layer height: 50%
First layer print speed: 50%
Z-Offset 1.5mm
Temperature First layer: 205°C
Fan off

IMG 20170312 223151 IMG 20170312 223153 IMG 20170312 223200 IMG 20170312 223245 IMG 20170312 223941 IMG 20170312 223957 IMG 20170312 224031 IMG 20170313 083456