I happened across an Openbeam Kossel Pro about 3 months ago, CHEAP, but I have still not been able to successfully make a print yet. I have tried to use matter-control but Octoprint has worked much better for me. Biggest problem right now is that the extruder temp can't hold and gives me thermal runaway errors. It is not overshooting, it will get to 200, start to print and 30 seconds or so later it starts to drops to 194 and can't keep, then it outputs errors and stops the print. I have run the PID tuning a bunch of times, no luck. The PID values are all over the place; doesn't matter the number of iterations, I have stored some of them with M301 and M500. I have no clue whats going on.
P - 45.33
I - 7.58
D - 67.77

P - 30.05
I - 4.22
D - 53.54

P - 38.36
I - 7.55
D - 48.72

P - 42.06
I - 7.33
D - 60.30

P - 44.41
I - 8.34
D - 59.12

P - 29.37
I - 5.52
D - 39.10

P - 17.99
I - 3.14
D - 25.79