Renaming library items takes several steps to ensure you are in the text field and any keyboard commands will not trigger tools/menu items.

Steps to reproduce:
1. Click on an object,
2. Drag to Library panel—often takes several times as noted in the video
(the libraries panel and new documents from libraries is flawed and not as efficient as Adobe Max presentations allude to, but that's another post)
3. After item successfully copied to Libraries, right click it in the libraries panel and click Rename
4. CLICK AGAIN ON THE TEXT FIELD OF THE LIBRARY ITEM
If you do not do this, and the object is still selected in the workspace, it will cause any characters on the keyboard you type to be recognized as keyboard shortcuts and NOT text.
5. You may have to click twice on the text field in the libraries panel.

I have a 2019 MBP i9 with Vega 20 GPU on macOS 10.14.6 so it's not a performance issue.

Please contact me directly if you need to hear about all the issues and feature requests for Libraries as it is an awesome tool but needs a lot of little work to make it as efficient as Adobe plans to be in 2020 and with their new initiatives.

Thank you for your products.