To reproduce:

1. Download attached "KeyboardTest-2018.4.8.zip" project and open in Unity
2. Build for iOS
3. Deploy the Xcode project to the iOS device
4. There will be 3 types of Input Fields (IMGUI, Unity UI, TMP) on the Screen
5. Tap on any of them to bring up the Keyboard
6. Press the physical sleep button on the device to lock it
7. Unlock the device
8. Hit "Ok" or "Cancel" on the Keyboard

Expected results: Keyboard is dismissed
Actual results: It is not possible to dismiss Keyboard

Notes:
- This issue reproduces only on iOS 13.* Devices
- Workaround: Tapping an Input Field again will allow the Keyboard to be dismissed
- The Customer thinks that Bug is related to image snapshot code in UnityAppController
- The Bug may also be related to "Render Extra Frame on Pause" project setting (enabling this setting causes the Bug)

Tested with:
- iPhone 8 Plus, iOS: 12.0 - Not Reproduced
- iPhone X, iOS: 11.3.1 - Not Reproduced
- iPhone XR, iOS: 12.0 - Not Reproduced
- iPad Pro (12.9-inch) (3rd generation), iOS: 13.1.2 - Reproduced
- VLNQA00277, Asus ROG Phone (ASUS_Z01QD), Android 8.1.0, CPU: Snapdragon 845 SDM845, GPU: Adreno (TM) 630 - Not Reproduced
- VLNQA00078, Motorola Nexus 6 (Nexus 6), Android 7.1.1, CPU: Snapdragon 805 APQ8084AB, GPU: Adreno (TM) 420 - Not Reproduced

Reproduced on Unity 2017.4.33f1, 2018.4.10f1, 2019.2.8f1, 2019.3.0b6 and 2020.1.0a8