Desk before and after printing the tray :-)
I had no object-fan on for the first 1.5 mm, only for the small cups. Sliced with Cura 3.6. My Kossel XL has Repetier 0.92.9 firmware.
The print with the blobs was printed with a Raspberry Pi 2 with OctoPrint 1.3.9 (default ping pong on) to feed the printer.
The print without the blobs (same GCODE) was printed with the same Raspberry Pi 2 and Repetier Server 0.90.7 (Image V13) (default binary protocol and no ping pong).
The blobs are caused by buffer underruns, which will make the printer stop for a short while, to wait for more data, and causing a small blob at each stop.