I think the issue is in the code 
https://cs.chromium.org/chromium/src/chrome/browser/ui/cocoa/location_bar/translate_decoration.mm

bool TranslateDecoration::OnMousePressed(NSRect frame, NSPoint location) {
  command_updater_->ExecuteCommand(IDC_TRANSLATE_PAGE);
  return true;
}

The code seems will always run the command command_updater_->ExecuteCommand(IDC_TRANSLATE_PAGE); even if it is already up.

We probably should change the code similar to
bool ManagePasswordsDecoration::OnMousePressed(NSRect frame, NSPoint location) {
  if (ManagePasswordsBubbleCocoa::instance())
    ManagePasswordsBubbleCocoa::instance()->Close();
  else
    command_updater_->ExecuteCommand(IDC_MANAGE_PASSWORDS_FOR_PAGE);
  return true;
}
in
https://cs.chromium.org/chromium/src/chrome/browser/ui/cocoa/location_bar/manage_passwords_decoration.mm

The problem is we need to find out is the TranslateBubbleController active or not but it is currently own by BrowserWindwoController and I have not figure out how to hold on to BrowserWindwoController  from translate_decoration.mm

I guess I need to use NSNotification to send notification from translate_bubble_controller.mm to  translate_decoration.mm about the translate bubble status.

We've discussed this elsewhere (sorry, no link handy right now), but:

All you need to do is make sure that a call to Show() will not re-show the bubble if there still is an existing one. (The focus loss of clicking on the icon will automatically close the bubble, but the variable holding the instance will not be reset until after Show is called again)

I propose two fixes:
1. https://codereview.chromium.org/2270913002/ (I think this is the right fix)
Looks like groby's earlier attempt to fix crash in bug/609446 cause this side effect.

2. https://codereview.chromium.org/2262913002/ (Please ignore this. This was my early hacky attempt)

Won't be launching the new UI on Mac