> I seem to be consistingly hitting this issue.

It will help with test development if you can provide a minimal example that reliably reproduces the problem. 

In msg353064 I see DuplicateHandle calls failing with ERROR_ACCESS_DENIED (5). Assuming the process handles have the required PROCESS_DUP_HANDLE access, it's most likely the case that the underlying NtDuplicateObject system call is failing with STATUS_PROCESS_IS_TERMINATING (0xC000010A). For example:

    import ctypes
    ntdll = ctypes.WinDLL('ntdll')
    from subprocess import Popen, PIPE
    from _winapi import GetCurrentProcess, TerminateProcess
    from _winapi import DuplicateHandle, DUPLICATE_SAME_ACCESS

    p = Popen('cmd.exe', stdin=PIPE, stdout=PIPE, stderr=PIPE)
    TerminateProcess(p._handle, 0)

Try to duplicate the process handle into the terminated process:

    >>> source = GetCurrentProcess()
    >>> target = handle = p._handle
    >>> try:
    ...     DuplicateHandle(source, handle, target,
    ...         0, False, DUPLICATE_SAME_ACCESS)
    ... except:
    ...     status = ntdll.RtlGetLastNtStatus() 
    ...     print(f'NTSTATUS: {status & (2**32-1):#010x}')
    ...     raise
    ...
    NTSTATUS: 0xc000010a
    Traceback (most recent call last):
      File "<stdin>", line 2, in <module>
    PermissionError: [WinError 5] Access is denied