I suspected it was a CPU error

[izard]

Every time I suspect I found a CPU errata, it ends up being something else. This time a compiler bug, again.
GCC 8.2.1, compiles _mm512_*fmaddsub*_pd intrinsics to vfmadd132pd instruction when compiling with -O0.

When compiling with -O1, -O2 or -O3 it compiles to vfmaddsub132pd, as expected. Happy debugging!