1. Open Any/New Project
2. Create and Animator by going to Assets>Create>Animator Controller
3. Open the created Animator Controller
4. Create a transition from Any State to any other state/Entry/Exit (this is not important as long there is an arrow from Any State to anything)
5. Select the transition line from Any State to another node
6. Drag the divider in between the side panel and the graph view. (see the attached video)

Expected result: the side panel can be resized and is released on mouse up.
Actual result: the splitter is still being moved after mouse up and remains that way regardless of user action. The following notification is printed to the console:

Should not grab hot control with an active capture
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)

Reproducible with: 2022.1.0a14, 2022.1.0a16, 2022.1.0b5, 2022.1.0b2, 2022.2.0a2
Not reproducible with: 2020.3.2.4f1, 2021.2.6f1, 2022.1.0a13

Note: in 2022.2.0a2, this behavior appears after selecting Any State and dragging the splitter or after a drag-selection in the Graph View. There is also nothing printed to the Console.