To reproduce:

1. Download and open "Assets.zip" project.
2. Navigate to Cookie->Scenes folder.
3. Open "Base" Scene.
4. Enter Play mode.
5. On the lower left side of the screen find the menu button and press it.
6. Then Find "Redeem Codes" button and press it.

Expected result: UI works as intended, no rebuild loop is caused, Input field is shown.
Actual result: Opening Object with Input field causes UI to go into rebuild loop and Input field is not shown.

Reproduced with: 5.6.0p1, 2017.1.0b1
Not reproduced with: 5.5.0f3, 5.5.3p1

Notes: Appears after an upgrade to 5.6. Uses TextMesh Pro plugin. Gif attached showing how to reproduce the issue.