<p>This work originally identifies a novel error mechanism, Oscillatory Rectification Errors (ORE), of the whole-angle mode gyroscope (WAMG) under oscillatory rotation and conducts important insights for WAMG based inertial navigation applications. Conventionally, WAMG is widely recognized as an ideal solution for high-dynamic measurement, but this study reveals significant inherent measurement risks in such scenarios with periodic motions. The dominant dynamic equation is firstly solved by using equivalent transformation and superposition principle. The conducted analytical solution clearly proves that the output of WAMG will drift to 3 attraction regions under oscillatory angular rates. There is a complex relation between the final bias state with its initial states, asymmetry parameters, and input signals, but the overall insight is that larger amplitude and lower frequency of oscillatory rotation, larger frequency difference, higher damping anisotropy degree, and less vibration energy will accelerate the drift process. This ORE is fatal for long term inertial navigation applications: the measurement output of WAMG will drift to certain bias attraction points under periodic motions. To intuitively demonstrate this phenomenon, a typical high precision hemispherical resonator gyro can drift 5.8156 deg in 10 hours, which is a severe hazard in navigation missions.</p>