@Glen_b Bugs go here: bugs.r-project.org/bugzilla3 but I'd probably enquire about this on R Devel first and if you don't get any response then file a bug so it isn't forgotten. If you are sure it is a bug, then you can go straight to bugzilla.

Thanks @Gavin. Quite, quite sure

But I think there's perhaps some benefit in posting to R Devel first.