This is a known bug for a long time by upstream, but it seems he does not care much about other software crashing because of this (like fore example libass). You can read more about this here: https://bugs.freedesktop.org/show_bug.cgi?id=79385 Reproducible: Sometimes
Created attachment 397482 [details, diff] This is the oficial patch upstream pushed to git
dev-libs/fribidi-0.19.7 is now in tree. Its thread-safe.