splines suddenly disappear when I scroll down UI

I have these nodes and spline placed in my gui at run time. Everything is working fine and with everything encased in a scroll box, i can scroll down. But a few inches down the page and all the splines dissappear. I just cant figure out why. If I scroll up again they all reappear.

was thinking clipping but it wouldn’t just turn them all off.

my BP:

my spline that gets instanced:

The node buttons remain on the screen all the way to the scroll bottom. But splines vanish. Am I making any obvious gaffs?

thanks, Sam