A strange visual Studio 2013 stop responding to a problem

The problem began yesterday, and it happened again today.

A suspected problem occurs when copying/pasting in a window that writes code (pending further confirmation of the trigger condition) and suddenly stops responding, and the following dialog box appears:

The text in the dialog box is:

Waiting for a required operation to complete. This dialog would close when the operation completes.

After a while, the dialog disappears and the status bar in the lower-left corner of the VS2013 shows the following status:

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The text of the status bar is:

Waiting for a required operation to complete ...

Visual Studio 20,131 Then is in this state without any response and can only force the end of the VS2013 process.

The VS2013 process was found to occupy about 50% CPUs at the end of the process.

Restart vs after ending the VS2013 process, all unsaved code is lost.

Initial suspicion is caused by the new configuration Sync feature of VS2013, which turns off the sync feature to see if the problem continues to occur.