Holographic Data Storage System (HDSS) is one of promising candidates for future high density Optical Data Storage (ODS) system. Modern HDSS using angularly multiplexed recording employs a complicated opt-mechanical system for controlling angle of the reference beam or disk positioning precisely and quickly to achieve high density and fast recording. However, mechanical instabilities during recording and involved degradation of signal quality in HDSS is one of the obstacles to prevent the technology from being a robust system. We analytically formulated effects of mechanical instabilities of a Galvano mirror and spindle motor on the HDSS by incorporating the concept of time averaged holography. Mechanical parameters such as amplitude and frequency of mechanical oscillation are related to optical parameters such as amplitude and phase of reference and signal beams. Through comparison of simulation results with experimental results, we confirmed that the developed optical model was able to predict signal level of a degraded holographic image due to mechanical instabilities. Then, the analytical formulation led to a new method of optical and post recovery for mechanical instability during recording hologram. The optical post recovery method enables a robust implementation of HDSS against mechanical instabilities.