@HuntleyBill Please post your sketchup file and the Gcode you generated.

 

Nothing wrong with the Gcode, so is probably a mechanical problem...
please reduce your acceleration (to half what they are now) rates for X and Y and run that again. if it then works ok, it means that
(one or more of)
a) the accel rate was too high for the power required
b) something is sticking somewhere, sometimes. (could be chips in the groove loading up the cutter, it is very small)
c) motor current is too low and could be higher
d) microstep setting could be reduced which gives more power. (have to adjust steps/mm to match!)

keen to see a video showing the entire machine, and some more info on the machine itself.

 

actually it is doing 6 passes. you set the material thickness to 5.1mm and the pass depth to 1mm, so the last pass is just .1mm deep. bit of a waste of time (-:
a possible solution is to do 5 slightly deeper passes

pass = 5.1/5 = 1.02mm​

or 6 slightly shallower passes

pass = 5.1/6 = 0.85mm
​

whether you choose bigger or smaller depends on how stiff and powerful the machine is.

Another thing to look at is feedrate relative to spindle RPM. We want to produce chips rather than dust. Chips tend to fly away while dust tends to pack into the slot. Recutting the dust is very bad for the tool and can also cause the flutes to pack full, then it stops cutting and can even catch fire.
So, we want to KNOW how big the chips are.

FR = RPM * T * CL​

Where:

• FR = the calculated feed rate in inches per minute or mm per minute.
• RPM = is the calculated speed for the cutter. (or just whatever your spindle does) (note1)
  
• T = Number of teeth on the cutter.
• CL = The chip load or feed per tooth. This is the size of chip that each tooth of the cutter takes.

For wood, CL is usually 0.05 to 0.25mm but with such a small cutter (you cnc file said 1.7mm) there may not be space in the flutes for bigger chips. So, my router does 24000rpm so I will use that, and assume a 2 flute bit.
FR = 24000*2*0.1

= 4800mm/minute​

wow, fast hey! so, you were feeding at 1800mm/m and that means the chips get smaller, dust, in fact.

(note1) : rpm is normally calculated from the cutting speed (how fast the tool edge goes past the material) and the diameter of the tool.
https://en.wikipedia.org/wiki/Speeds_and_feeds
from that page, for a 1.7mm bit the spindle should be doing 34242RPM at the LOW end of the SFM for wood.

PS: you should read the SketchUcam manual to learn about the interaction between material thickness and 'overcut%' settings.
hit the big blue question mark in the toolbar

 

I have just run it through UGS 1.0.9 driving GRBL v1.1f and it completes without error.