if nftables-0.5 and gentoo-sources-4.6.2 are used : nftables segfaults on rule load. (Only tested with my complex rules, not with simple ones) updating to nftables-0.6 fixes it.
Insufficient information to investigate bug and nftables-0.5-r4 has been superseded by nftables-0.6-r1. If the issue persists with new version feel free to post a new bug.