Steps to reproduce:

1.  Open a new project
2.  Add a scoped registry (Edit > Project Settings > Package Manager - Scoped Registries section)
3. In Package Manager window add any unsigned package by name

or

1. Open any Project
2. Sign out of Hub
3. Observe the License pop up
4. Log back in to Hub
5. Close the pop up
6. Resize Window

or (for 6000.0.13f1)

1. Open any Project
2. Return license in Hub
3. Observe the License pop up

Actual results: 
A pop up for unsigned package has appeared which is not rendered properly and no buttons are visible in the window
Editor's buttons start artifacting until they are redrawn
Package Manager might not render properly on second opening, Editor has to be restarted
Other Editor Windows might break

Expected results: 
A pop up for unsigned package has appeared and rendered correctly with visible buttons

Reproducible with versions: 
6000.0.13f1, 6000.0.64f1, 6000.2.15f1 (Can be reproduced with the "License Removed" pop-up),6000.3.0a5, 6000.3.1f1, 6000.4.0b1, 6000.5.0a3

Not reproducible with: 6000.0.12f1

Tested on (OS): 
Ubuntu 22.04
Ubuntu 24.04

Notes:

•  Works as expected on MacOS and Windows
• Closing the pop up window still imports the package
• This also affects other pop ups, e.g. When a license is removed