Seems you are not of the ones who got troubles with 29v updates.
Before I've got the latest WinOS and OBS updates, my stream rig was perfect with xeon e5 v3 wich used medium preset with some x264 options. After updates my rig can't render anymore with medium preset, and streaming still possible with faster preset only!!!
Oldest 28.x (xeon e5v3) -> Medium
Latest 29 (xeon e5v3) -> Faster
... excellent updates.. mega updates :\
p.s. after downgrade problem not solved, so I thinking the problem with win32 updates or with prefetcher