TinyG reporting "Arc specification error" on a G1 command

[denverh2000]

I'm doing a CNC conversion on a Taig mill. At this point I don't yet have the motors attached to the mill, but I do have them connected to a TinyG. Everything seems to work fine, except that I keep getting odd errors if I create toolpaths using arcs. I'm using Vectric's Aspire for that, and cncjs to send the gcode to the TinyG. Here is the tail-end of the output from the serial console window:
feeder> G0 Z0
{"sr":{"vel":506.77,"posx":-0.701,"posy":0.005,"mpox":-0.701,"mpoy":0.005}}
{"r":{},"f":[1,0,6,4399]}
{"sr":{"vel":400.01,"posx":-0.484,"posy":0.004,"mpox":-0.484,"mpoy":0.004}}
{"qr":30}
{"sr":{"vel":134.87,"posx":-0.086,"posy":0.001,"mpox":-0.086,"mpoy":0.001}}
{"sr":{"vel":6.46,"posx":-0.001,"posy":0.000,"mpox":-0.001,"mpoy":0.000}}
{"qr":31}
{"sr":{"vel":12.32,"posx":0.000,"posz":-1.497,"mpox":0.000,"mpoz":-1.497}}
{"sr":{"vel":147.30,"posz":-1.370,"mpoz":-1.370}}
{"sr":{"vel":291.79,"posz":-0.998,"mpoz":-0.973}}
{"sr":{"vel":294.72,"posz":-0.502,"mpoz":-0.502}}
{"sr":{"vel":156.81,"posz":-0.117,"mpoz":-0.117}}
{"sr":{"vel":12.32,"posz":-0.002,"mpoz":-0.002}}
{"sr":{"vel":0.00,"stat":3,"cycs":0,"mots":0,"posz":0.000,"mpoz":0.000}}
{"qr":32}

G1Z-1.500F914.4
{"err":{"code":155,"msg":"Arc specification error","line":223,"data":"G1Z-1.500F914.4"}}

Here are a few lines on either side of line 223:
219 G2X28.028Y36.966I38.818J-33.977
220 G0Z12.700
221 G0X-93.980Y0.712Z12.700
222 G0Z2.540
223 G1Z-1.500F914.4
224 G2X-93.268Y-0.001I0.000J-0.713F400.0
225 G2X-93.980Y-0.713I-0.713J0.000
226 G2X-94.693Y-0.001I0.000J0.713
227 G2X-93.980Y0.712I0.713J0.000

Any idea why this error is occurring?

Regards,

Denver