From this log 2016-12-18 18-05-08.txt:
18:07:08.816: Output 'simple_stream': Number of lagged frames due to rendering lag/stalls: 28 (22.2%)
This was made with Ultrafast encoding profile
Your CPU can´t handle encoding
Reduce to 30 FPS.
If no lag, yo can try Superfast to get better image.
By the way, you are on a MAC
18:05:10.111: OBS 0.16.2 (mac)
This is WINDOWS support section.
I don´t know how to encode with your MAC GPU, if possible.
This could be the solution.