Reproduction steps:
1. Open the attached “steamdeck_bug” project
2. Click File > Build Settings… > Build
3. Launch the player in SteamDeck Gaming mode
4. In Player, focus on the Text Field
5. Bring up the Steam on-screen keyboard with Steam+X
6. Type in lowercase characters and observe the Text Field
7. Tap Shift twice to lock it, type in characters, and observe the Text Field
8. Unlock Shift, enable Caps-Lock, type in characters, and observe the Text Field

Expected results: All pressed characters, be they lowercase, uppercase, numbers, or special characters are entered in the Text Field
Actual results: Uppercase characters and special characters are not entered

Reproduced with: 6000.0.50f1, 6000.1.6f1, 6000.2.0b3
Not reproduced with: 2022.3.63f1

Reproduced on: SteamDeck (SteamOS 3.7.8, native Linux build), Ubuntu 24.04 (Steam Big Screen mode)
Not reproduced on: SteamDeck (SteamOS 3.7.8, Proton 9), Windows 11 through Steam Big Screen mode (the results are entirely different there as the on-screen keyboard only inputs one character and resets that character to the newly clicked one)

Notes:
- Couldn’t find regression point because of long testing time for each build
- This is reproducible from Steam Big Screen mode on Ubuntu. Select the text field when launching the player through it, and then open the Steam Quick Settings. There you will find a button to bring up the On-Screen keyboard.