Comparisons of the conjugate closure trace phases across the three observing campaigns for two quadrangles. Deviations from arg(𝒞) = 0 indicate the presence of significant polarization structure, independent of leakage and gain calibration. Closed and open points show low- and high-band data, respectively, offset in time for clarity. The model predictions from the low-band reconstructions described in Sect. 3 are shown for reference (for the Bayesian methods, THEMIS and Comrade, the 95-percentile range is shown along with five draws from the posterior). Note the variation in the vertical axis ranges between panels. Because LMT did not observe during the 2021 campaign, we show the ALMA-PV-NOEMA-GLT quadrangle in 2021, for which clear deviations from zero are apparent.