Direct comparison of the GRAVITY and MATISSE closure phase observations taken on two overlapping nights, 24 and 25 January 2021 (≈ 59238.5 MJD). Panels A-D: Measurements for the four sets of baseline triangles, with an inset plot in the corner showing the corresponding (u, v) coordinates in meters. The solid line shows our binned data, while the dashed and dotted line show the simulated data of the best-fitted skewed ring for these dates with corresponding θ_skwPA for MATISSE (≈ 92°) and GRAVITY (≈ −173°) respectively; see Fig. 7. Panels E and F: The ${\chi }_{\mathrm{r}}^2$-maps for the fitted asymmetry parameters, together with a representation of the best-fit direction for the respective bands.