How to reproduce:
1. Open any Unity project
2. In the Hierarchy window, create two parent GameObjects with some children (so there are two foldouts in the Hierarchy)
3. Select the upper parent, press the right arrow key twice

Expected result: the selection moves to the first child after the foldout is expanded
Actual result: the selection moves to the next foldout in the Hierarchy without selecting the first child of the first foldout

Reproducible with: 5.6.2p4, 2018.4.24f1, 2019.4.2f1, 2020.1.0b14, 2020.2.0a16

Note:
1. Reproduced in the Project Settings window and the Hierarchy window, but may not be limited to those windows only.