Does she go up the ramp and leave her babies behind or does she hang out with them outside?
I was catching the ducklings to put them into the house at night, but they are terrified of me and mama would attack me and my run isn’t tall enough to stand in and they pooped all over me so I said screw it, they can sleep outside if they can’t figure it out!! Well, wouldn’t you know, by total dark, mama and the babies were all in the house. So I guess they use the ramp when I’m not looking! Honestly mama will teach them and they will figure it out. If the run is secure, don’t worry too much. You could put some carpet or shelf liner on the ramp to make it a bit more grippy if you want.