mcmc_pairs bivariate off-diagonal plot axis incorrect.

Data file: https://drive.google.com/open?id=1pnAUDCz9uscccSaUISodF9cqGF23uNzU

Off-diagonal bivariate scatter plot axes are out of line

My understanding from the documentation is that half the chains are used for each of the off-diagonal plots. In this example case (see posterior data file linked above) the chains have not converged and so the lower off-diagonal plot seems to be using chains that only sampled from one mode, using default condition I think this should be correct. I believe the x-axis should be inline with the above univariate marginal plot and the y-axis inline scaled as the x-axis of the upper off-diagonal bivariate plot?

load(file = "posterior.arr.RData")
mcmc_pairs(posterior, pars = c("u","v"))