Please file an issue on R8 at https://issuetracker.google.com/issues/new?component=326788 and link it here. It's unlikely that OkHttp is actually the cause of this beyond having a shape of code that somehow breaks R8.
Also, make sure you're on the latest Android Gradle plugin. I don't have any problems on 3.4.1 or 3.5 betas with the RC1.
If others come across this - issue can be tracked here.
still have this problem on rc1 with lastest gradle 3.4.1. I need to revert to use 3.14.2
@namkazt Just disable advanced profiling in your run configuration and the problem will be gone.

@bohsen ohhh right, I wonder why it just happens from nowhere when just run normally. Thanks