What scalability settings are you currently using? In addition, what steps can I take to recreate this on my end?
I tried several convinations of scalability settings with no effect, in 4.12.5 and 4.13.0 in the flicking. I can say the static meshes does not flick, just some actors as i say before.
Here there is a unanswered question about the same: His specs are pretty similar to my mac.
I have good news. I looked through our system and found that this is a known issue with Intel graphics cards on Mac, and is in our system as UE-27525. Additionally, this has already been fixed internally and is scheduled to be released in 4.14.
These are very good news, when is planning the release of 4.14, the 4.13 is still young 
Thank you ver much.