ix-tree in dropdown, tree elements disappear after scrolling

[sire987]

Prerequisites

• I have read the Contributing Guidelines.
• I have not leaked any internal/restricted information like screenshots, videos, code snippets, links etc.

What happened?

Unfortunately, we have noticed that some tree elements of the ix-tree disappear when it is built into an ix-dropdown-button.
How it behaves:

• Opening the dropdown
• scroll to the bottom half of the list
• click on any element
  --> the upper part of the tree has now disappeared
• scroll to the first visible element
• click on it
  --> a few “lost” elements now appear again at the top

How it should behave:

• no disappearing or appearing elements...

What type of frontend framework are you seeing the problem on?

Angular

Which version of iX do you use?

v2.7.0

Code to produce this issue.

https://stackblitz.com/edit/j8h8x4-c1yqqfmw?file=src%2Fapp%2Fapp.component.ts