Calling start and then end too quickly causes dismiss to fail

[mylogon341]

I am running

    let ringParam: RingProgressorParameter = (.endless, UIColor.black.withAlphaComponent(0.9), 80, 5)
    Prog.start(
        in: window,
          .ring(ringParam),
          .custom(identifier: viewId, parameter: ["text": text])
      )

and the API is responding very quickly, so I call

    Prog.end(in: window) {
         complete?()
      }

the spinner is disappearing, but the translucent view is remaining, overlaying my window. To get around this, I need to synthetically delay end by 1 second before dismissing, which isn't great.