As I wrote in issue #3 ... there is problem in your code you should fix, notably as it fixes the slightly change plot.default() function in the development version of R (aka R-devel):
https://www.r-project.org/nosvn/R.check/r-devel-linux-x86_64-fedora-gcc/SortedEffects-00check.html
The following patch (aka "diff") is against the CRAN version of R/spe.R .. possibly differing from the outdated current GH version:
--- SortedEffects_CRAN/R/spe.R 2021-09-01 02:13:18.000000000 +0200
+++ SortedEffects/R/spe.R 2025-09-05 11:36:18.974462587 +0200
@@ -320,8 +320,8 @@
us <- x$us
alpha <- x$alpha
xlim <- range(us)
- plot(us, SE[[1]], type = "l", xlim, ylim, log = "", main, sub, xlab, ylab,
- col = 4, lwd = 2)
+ plot(us, SE[[1]], type = "l", xlim=xlim, ylim=ylim, log = "",
+ main=main, sub=sub, xlab=xlab, ylab=ylab, col = 4, lwd = 2)
polygon(c(us, rev(us)),c(SE[[2]], rev(SE[[3]])), density = 60, border = F,
col = 'light blue', lty = 1, lwd = 1)
lines(us, SE[[1]], lwd = 2, col = 4 )
I assume you are aware that it is very unsafe, not to name arguments in a function (apart from the first or first two, typically);
even more so when the function is a generic function as plot() where you make assumption about the default method plot.default() and its exact order/position of arguments.