Getting a mobile prototype to stop bouncing around

I’m developing a mobile prototype, sized for an iPhone 6. The sizing is correct. However, on the phone, I can drag the whole layout around about 100px in any direction. I want to prevent that.

Under Generate HTML on the Mobile/Device section, I’ve got “prevent vertical page scrolling” selected. That doesn’t seem to make any difference with this.

On the Mobile/Device tab, select the Include Viewport Tag checkbox, then set:
Width: “device-width”
Initial Scale: 1.0
Minimum Scale: 1.0
Maximum Scale: 1.0
User Scalable: no

Thanks for that. Unfortunately, I’ve got another situation going on: I didn’t originally size the layout for the device I want to test on (iphone 6/7/8). So as to avoid having to go into every single element and resize it, I was hoping to use the scale settings on the mobile/device tab.

So, where you prescribe 1.0 for those 3 scale settings, I’ve used 1.2. That sizes the layout perfectly. However, it still moves all over the screen if you drag it around.

I can go in and resize all the elements. That will take half a day so I’m going to pursue every other option first. But if you think the only way to stop the scrolling is for all scale settings to be 1.0, I’ll try that.