Huge EditorOverhead Time in profiler in 2018.2. No idea what's causing it.

I've been using unity since ~4.6 and never had so many obscure, ungoogleable issues as I have in 2018.2.

I'm using 2018.2.4f1 and now even in recently made and even new and empty projects my EditorOverhead in the profiler when I hit play is 800-1000ms, causing a big hangup when playmode starts before whatever it is that's happening stops.

Also,

I'm getting this: Unaccounted time between file.open and enterplaymodeprestart

I can't imagine what's causing it, and I feel like they're related. It also occurs even in new and empty projects.

The peculiar part is, however: In an old project that I haven't touched since 2017.4 with very complex scenes and thousands of files, when I open it in 2018.2, the 800+ms editoroverhead doesn't happen (the usual 90-140 happens) and I don't get unaccounted time between either.

In fact, any project whose solutions were created in 2018.1 or earlier does not have this issue. Only new 2018.2 projects or projects with solutions updated to 2018.2 are having this issue.

It's baffling, but I can't continue until I know what's going on or what I might be doing wrong somehow.

Thanks!

 

After profiling the editor also while entering playmode, I've found that
ApplicationTickTimer
>EnterPlayMode
...>Console.Open()
...>>FileStream..ctor()
...>>>PackageManager.Initialize is what's taking 3000ms upon entering playmode

Don't know what to do with that information. Package Manager is unique to 2018, which could be relevant.

Is there a reason PackageManager needs to initialize when entering playmode? I don't understand.