Updating auto-scale in arm hostpool

I am running the put for auto-scale with the properties for bypassing drain mode 

        "userDriven": {
            "stopDelayMinutes": 10,
            "minAvailableSessions": 0,
            "bypassDrainMode": true
        },
        "autoScaleTriggers": [
            {
                "triggerType": "UserDriven",
                "averageSessions": null,
                "availableSessions": null,
                "cpu": null,
                "ram": null,
                "userDriven": {
                    "stopDelayMinutes": 10,
                    "minAvailableSessions": 0,
                    "bypassDrainMode": true
                },
                "personalAutoGrow": null,
                "personalAutoShrink": null
            }
        ],

I get a success back from the API, but it does not appear to make the changes. If I check the box in the UI and check the JSON then it is correct. It seems like the API works fine to update other settings, just not this one. Is there something that I'm doing wrong?