Marked will not fix back in unity 5.5.3f1 and is still present in every version since. Despite it saying magnetic scroll view. I find it affects any scroll view 100% of the time. Layout components sometimes may crash on the undoing of a child creation undo action. Though may also be due to having a scroll view in the scene, regardless of the layout group not being in the scroll view. It's also not just panels but seems any child object being created and removed with undo will crash unity. Seeing as you will likely test spacing and look and feel by duplicating your child object. You are likely going to undo and crash under these conditions. You likely hadn't just saved. You may not put together what happened to find this. If you did I'm sorry I feel your pain. Even knowing about this bug since September. Likely hitting it many times before putting together what happened leading me here. I still find myself getting sucker punched by this on occasion. Knowing about it has helped minimize my work loss. Though I'm sure I have not found all the ways to trigger this crash yet. Sorry friend, low priority.

Just ran into this myself. So the official response is just don't undo after adding things to a scroll view? I mean this is a pretty big workflow killer. The most likely way you hit this crash is by spending time designing your list item. Duplicating it to check your scroll view spacing. Then boom undo causes all that work to go down the drain if you haven't saved step by step or recently. So your low priority defect. Is actually a time killer considering I did this twice before coming out to find it's a bug and not set to be fixed.