Can't quit iTunes normally I am using 10.12.5 and iTunes 12.6.1.27. Whenever I quit iTunes it will hesitate, the main window disappears but the menu bar remains, but the process keeps running and the icon in the dock shows it's still there. And a click on the icon and the window reappears. In Activity Monitor iTunes won't disappear, but it doesn't show any %CPU, then it almost immediately reappears. It will force quit.

I don't have any plugins for it. Same result even if iPhone, iPad aren't connected. I've deleted prefs and reinstalled iTunes. It WILL quit if I restart in Safe Mode.

I looked at Console,and I get stuff like this:

    NSApplicationBundleIdentifier = "com.apple.iTunes";
        NSApplicationName = iTunes;
        NSApplicationPath = "/Applications/iTunes.app";
        NSWorkspaceApplicationKey = "&lt;NSRunningApplication: 0x7fc1e713b030 (com.apple.iTunes - 12343)&gt;";
Jul  8 10:37:54 riMac iTunes[12576]: Entered:_AMMuxedVersion2DeviceConnected, mux-device:3
Jul  8 10:37:54 riMac iTunes[12576]: Entered:_AMMuxedVersion2DeviceConnected, mux-device:2
Jul  8 10:37:54 riMac iTunes[12576]: Entered:_AMMuxedVersion2DeviceConnected, mux-device:1
Jul  8 10:37:54 riMac iTunes[12576]: tid:1103 - unable to query device capabilities
Jul  8 10:37:54 riMac iTunes[12576]: tid:1a203 - unable to query device capabilities
Jul  8 10:37:54 riMac iTunes[12576]: tid:1303 - unable to query device capabilities

Jul  8 10:38:21 riMac iTunes[12576]: _send_message (thread 0x700005e4f000): Could not securely send message size 443: SSL_ERROR_SYSCALL errno (Broken pipe).
Jul  8 10:38:21 riMac iTunes[12576]: _send_message (thread 0x7fffb4a963c0): Could not securely send message size 406: SSL_ERROR_SSL (error:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry).
Jul  8 10:38:21 riMac iTunes[12576]: AMDeviceStopSession (thread 0x7fffb4a963c0): Could not stop session with device 2: kAMDSendMessageError


Ideas?
I figured it out. For those who have the same problem, it was Cindori's Command Center utility. Repeatable on my machines: iTunes won't quit with CC running; will quit if CC isn't running. CC has a function to control iTunes; should have remembered that.