How to read MongoDB .mdmp files
You might want to consider opening an issue on MongoDB's Issue Tracker and providing the *.mdmp file in the issue.



*.mdmp files are considered to be Microsoft Dump Files. 


  Compressed file created by Windows after a program error or crash; contains data "dumped" from the program's memory space; saves information about the error, which can be used for debugging; commonly created along with an uncompressed .HDMP file and can be sent to Microsoft as part of a bug reporting process.


Reference: .MDMP File Extension (fileinfo.com)

If you have a Microsoft debugger and the symbols for the relevant progams, then you can have a look at the dump file yourself:


  A dump file is a snapshot of an app at the point in time the dump is taken. It shows what process was executing and what modules were loaded. If the dump was saved with heap information, the dump file contains a snapshot of what was in the app's memory at that point in time. Opening a dump file with a heap in Visual Studio is like stopping at a breakpoint in a debug session. Although you cannot continue execution, you can examine the stacks, threads, and variable values of the app at the time the dump occurred.


But be aware:


  Debugging dump files of optimized code can be confusing. For example, compiler inlining of functions can result in unexpected call stacks and other optimizations might change the lifetime of variables.


Debugging a kernel-mode dump file requires you to...


  To debug kernel-mode dump files in Visual Studio 2013, download the Windows 8.1 Version of Debugging Tools for Windows. See Kernel Debugging in Visual Studio.


Reference: Using Dump Files (Microsoft MSDN)



There are some third-party tool from NirSoft that might help in finding the culprit. 

And then there is the following list that tells you which tools could possibly open the *.mdmp file for you:

.mdmp Extension - List of programs that can open .mdmp files (Extension NirSoft)


  Disclaimer:
  I am in no way affiliated with NirSoft. I only use their software.