New (minor) version of R was released a few days ago... Announcement at https://stat.ethz.ch/pipermail/r-announce/2017/000611.html
Bumped locally and haven't had any problems for a couple of weeks now.
Superseded by release of =dev-lang/R-3.4.0, see bug https://bugs.gentoo.org/show_bug.cgi?id=616436
=dev-lang/R-3.4.1 is now in Portage.