This can be performed with event listeners + a set timeout after the event listener (if your onboardng is made with forms or action buttons).
In your case one checkpoint = one event listener.
Without a full overview of your onboarding setup => I won’t be able to make anything (And I don’t have time to check unfortunately).
But here is an additional code with the right event listener attached to a form. This example might give you some clue to perform what you want (the spinner is replaced by an alert box in this use case).