UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.81 Safari/537.36

Steps to reproduce the problem:
This is not a great bug report because I am unable to reproduce it consistently. It only occurs when using the debugger - the code itself actually runs fine. It's as if devtools thinks all my variables are out of scope when they're not.

What is the expected behavior?

What went wrong?
Have a look at this video:

https://i.imgur.com/lmhKJoP.mp4

Notice that every local variable is showing as undefined. And notice that the debugger statement should only have triggered if the two variables were different. So devtools is lying about them being both undefined.

It's also impossible for `Number(...)` to return undefined, so that's just extra evidence that devtools is wrong here.

Did this work before? N/A 

Chrome version: 69.0.3497.81  Channel: n/a
OS Version: 16.04
Flash Version: 

I have also tested this on Chrome 70.0.3538.16 (Official Build) beta (64-bit). I get the same result.

If I can get around to stripping down my code to try to get a minimal example, I will, but I might not be able to.