Compiler generated unexpected `IN AL, DX` (opcode `EC`) while setting up call stack

Sounds like you are using VS2015. Your conclusion is correct, its debugging engine has a lot of bugs. Yes, wrong address. Not the only problem, it does not restore breakpoints properly and you are apt to see the INT3 instruction still in the code. And it can't correctly refresh the disassembly when the jitter has re-generated the code and replace stub calls. You can't trust anything you see.

I recommend you use Tools > Options > Debugging > General and tick the "Use Managed Compatibility Mode" checkbox. That forces the debugger to use an older debugging engine, VS2010 vintage. It is much more stable.

You'll lose some features with this engine, like return value inspection and 64-bit Edit+Continue. Won't be missed when you do this kind of debugging. You will however see fake code addresses, as was always common before, so all CALL addresses are wrong and you can't easily identify calls into the CLR. Flipping the engine back-and-forth is a workaround of sorts, but of course a big annoyance.

This has not been worked on either, I saw no improvements in the Updates. But they no doubt had a big bug list to work through, VS2015 shipped before it was done. Hopefully VS2017 is better, we'll find out soon.

As Hans's answered, it's a bug in Visual Studio.
To confirm the same, I disassembled a binary using IDA 6.5 and Visual Studio 2019. Here is the screenshot:
enter image description here

Visual Studio 2019 missed 2 bytes (0x55 0x8B) while considering the start of main.

Note: 'Use managed compatibility mode' mentioned by Hans didn't fix the issue in VS2019.