presets: Minor encoder tweaks for main Production presets.
Add additional x264 encoder options dct-decimate=0 and fast-pskip=0 (same as no-dct-decimate=1 and no-fast-pskip=1).
In some special cases, reproduction of flat areas and subtle gradients may improve slightly. Generally speaking, any change should be visually imperceptible at these bit rates, but adding a few extra bits is always acceptable when encoding for production intermediate purposes. Negligible speed hit (1-2%) for the main Production presets.
On the contrary, these settings are worse than useless for Production Proxy presets, which are optimized for speed. 5% speed hit isn't worth the tradeoff for low resolution proxies that need to be generated quickly and won't be used for final export.