The _avx2 binary of the 4.0 release accidentally contains a handful of AVX-512
instructions in the NNUE evaluation path (a build-script flaw on my side). On
CPUs without AVX-512 (your Kaby Lake, and anything pre-Ice Lake / pre-Zen4)
the engine starts, answers UCI, and dies with an illegal instruction on the
first evaluation, which matches your "crashes after 2-3 seconds" and Arena
showing Hash=0 exactly.
A fixed _avx2 binary (verified clean of AVX-512 this time, with an automated
check added to the build pipeline) is being rebuilt right now and I will
replace the release asset shortly.

