I had a similar problem that seemed to stem from using the Content Size Fitter component on the content that I wanted to scroll. I could set the Scroll Bar’s Value to 1 but it would always reset itself to 0.5.
THE FIX: In the Rect Transform component of your scrollable content the Pivot Y value is probably set to 0.5. Change this Pivot Y value to 1. That should force your scrollable content to always start from the top.
OK I set a check to record the menuOpenTime then in Update checked Time.time to see if it was > menuOpenTime + 0.1f.
Still failed so set that to 0.2f and it fixed it.
No idea why it always works first time then menu opens but on subsequent times it fails unless I check it. The menu is doing exactly the same thing each time I open it but 100% of the time it works when the menu first opens but fails on all occasions I open it after that.
This is just a test scene but in reality I’d want to stop time when in menus so I suppose I’d need to count passed time with fixedDeltaTime.
Maybe something that needs fixing in the UI but then it’s still early days for the new UI.