By using synchrotron X-ray diffraction, we investigated the in-plane distribution of preferential glide planes in a metamorphic InGaAs solar cell with a relatively low open-circuit voltage (V oc) compared to other cells fabricated on the same wafer. The reciprocal-space maps revealed that the low-V oc cell contains several domains with different preferential glide planes of β dislocations. Since fluctuations of the average β-glide plane have not been observed for high-V oc cells, the observed inhomogeneous distribution should be related to the V oc degradation. Understanding preferential glide-plane changes within a cell can help to improve the uniformity of cell properties over the whole wafer.