How to reproduce:
1. Open the attached project
2. In the Build Settings, switch the Target Platform to UWP
3. Build the project
4. Open the solution .sln file in Visual Studio
5. Run the build on the Local Machine (Debug | x64)
6. Once the project is launched, enter "abc" to both input fields (Unity and TextMesh Pro)
7. Using the mouse, place the caret between letters "b" and "c" (in both Input Fields)
8. Type "ddd" (in both Input Fields)

Expected result: In both Input Fields, placing the caret using the mouse works, and text can be added within the existing text.
Actual result: In TextMesh Pro InputField, placing the caret using the mouse no longer works, also text can only be appended to the end.

Reproducible with - 2019.1.0a8, 2019.1.0a14, 2019.2.0a1
Not reproducible with - 2018.3.3f1, 2019.1.0a7

Note: Inside the TextMesh Pro InputField, the caret position can still be changed using the keyboard arrow keys. (However, the newly typed text still appears at the end.)