Make sure that Setting 34, 4th Axis Diameter, and Setting 79, 5th Axis Diameter, are both set to the correct diameter. The default value in these settings is 1.
If the diameters are not correctly set, you could get unusual results.
For example, if Setting 34 and Setting 79 are set to 1 when the part has a 3 inch diameter, the actual feedrate around the circumference of the part is (3) times faster than the programmed feedrate. This can cause problems with the surface finish. Or, this can cause broken tools.
For example, if Setting 34 and Setting 79 are set to 3 when the part has a 1 inch diameter, the time to machine the part is (3) times longer than usual.
It is also possible that the programmed feedrate is higher than the rotary's capability.
Make sure the rotary feedrate is not higher than the maximum degrees-per-minute (DPM) specification. Refer to the advertised specification. Calculate the DPM from the programmed feedrate and diameter.