It happens that you need to find issues, yes, trust me it happens even for me… and here is how:

To enable VMM debug logging, use the following steps:

• Create a folder called C:\vmmlogs.
• Open an elevated PowerShell window on the VMM server or host computer and run the following commands (the second command may wrap in your display):

logman delete VMM

logman create trace VMM -v mmddhhmm -o $env:SystemDrive\VMMlogs\VMMLog_$env:computername.ETL -cnf 01:00:00 -p Microsoft-VirtualMachineManager-Debug -nb 10 250 -bs 16 -max 512 -a

• Start the trace by typing the following command in the elevated PowerShell window:

logman start vmm

• Reproduce your issue.
• As soon as you reproduce your issue, stop the trace by typing:

logman stop vmm

• Switch to C:\vmmlogs. 
• To convert the trace, type the command:

Netsh trace convert <filename>

• Read file, find issue, fix, have a nice day.

The original post from Microsoft is here

/mike