Motor errors at slow feed

I have a 3 amp stepping motor on my x axis it runs well with jogging
and with single g00 and g01 moves. Although it growls when I use
feeds less then 20 it still moves correctly.

When I execute the following coordinated movement it jitters, growls
and misses steps:

G0 G49 G40 G17 G80 G50 G90
M6 T0(TOOL DIA. 0.4375)
G64
G20 (Inch)
M04 S0
G00 G43 H0 Z0.5
X0 Y0
G01 Z-0.0040 F10
G2 Y0 X0.2625 R0.1313 F10 <- movement is fine here
Y0 X-0.2625 R0.2625 <- errors and noise start here

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