@Magik Mark
I've looked at commits 2.8+48 (b0d31e2) and 2.8+49 (5d34bbf). In version +49 there is potentially dangerous change from one (atomic) 32-bit operation to two 16-bit operations. I've reverted these changes -- you can test if patched version 2.8+58 hangs or not (patch file inside)
http://www.msystem.waw.pl/x265/x265-...vs2017-AVX2.7z