On Mac, I was experiencing garbled console output and lower than expected fps. More signs of trouble: starting the profiler would error with some "could not read firmware version error" etc.
Console output looked like a bunch of ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ ÿÿ characters
So I thought: "
let's update the sdk and restart my mac. THAT will fix it.". So, while I was closing all open apps, at some point I ran into Mirror. 
After closing Mirror, it was all systems go 
Easiest and most effective optimisation session ever.
So yeah, make sure you are not running Mirror lol.