Generate Output with Start Triggering

I am hoping to generate a synchronized output signal on PFI1 for each incoming trigger:

scopeSession.ExportedSignals.StartTriggerOutputTerminal = ScopeStartTriggerExportedOutputTerminal.Pfi1

However, I had only a low rep rate trigger output on PFI1 that is out of sync with the incoming trigger signal, as you can see here (yellow trace is the trigger input and blue trace is the PFI1 output. What did I do wrong here?

Thanks in advance.