GitHub Bug: https://github.com/Unity-Technologies/InputSystem/issues/351
This happens in the Input Action UI. The Interactions have more input field takes "infinity" as valid value. And if user switch focus, that invalid input causes FormatException in the console, and the Property tab turns blank, stopping user from correcting the mistake or making any change. The only workaround is to either delete the Action or Binding with the issue and make the same one again, or discard all changes if they haven't saved after the issue happens.
Another problem is when a small number is used as input, such as 0.00001, it is automatically transformed into e-notation, like 1e-05. The same FormatException is thrown, and the Property tab turns blank.

Repro:
1. Download project and package at: https://github.com/Unity-Technologies/InputSystem
2. Open with 18.3 or 19.1
3. Open InputAction at: Demo -> SimpleDemo -> SimpleControls
4. Choose "PrimaryAction" under "fire" in the middle section
5. In the right section, click on Tap or Slow Tap under the Interactions.
6. Put "Infinity" or "0.00001" in the input field underneath
7. Click on anything else in the middle section
8. Click on the "PrimaryAction" again
9. Observe the right section in the UI and Console window in the Editor

Actual: The Input Action UI doesn't handle "Infinity" and e-notation, causing FormatException and partial UI lock-down.
Expected: Turns "infinity" into 0, like how it handles "a" or "#", and recognizes e-notation number if float is allowed.