Reproduction steps:
1. Open the attached "test_1636964" project
2. Open the "Assets/Test.unity" Scene
3. Enter the Play Mode
4. Input "1000"
5. Move the caret to a position between the second digit (which is '0') and the third digit (which is also '0')
6. Observe the caret

Expected result: Caret is visible
Actual result: Caret disappears

Reproducible with: 3.2.0-pre.1, 3.2.0-pre.12 (2022.3.60f1, 2023.2.0a13), (Built-in) 2023.2.0a14, 6000.0.48f1, 6000.1.2f1, 6000.2.0a10
Not reproducible with: 3.0.9 (2022.3.60f1, 2023.2.0a13)
Couldn't test with: 4.0.0-pre.1 (2023.2.0a13) error CS0029: Cannot implicitly convert type 'uint[]' to 'int[]', 4.0.0-pre.2 (2023.2.0a13) warnings Font Asset was not found

Reproducible on: Windows 11
Not reproducible on: No other environments tested

Notes:

• Reproducible in Player
• Caret disappears both when selecting its position with the mouse cursor and when moving it with the arrow keys
• Discussions thread: https://discussions.unity.com/t/the-input-field-caret-size-varies-can-disappear-if-width-1/1636964