Reproduction steps:

1. Open "UIBug.zip" project
2. Open "Test" scene
3. In the Hierarchy window go to "Canvas" -> "Item" and switch "RedBox" and "BlueBox" position in the hierarchy
4. Enter Play more

Expected Result: The Red and Blue boxes should stay in the same position within the "Item" GO (Use workarounds to see correct behavior)
Actual Result: The "RedBox" Rect Transform gets unexpected values

Fixed in: 2018.1.0b5

Reproduced with: 2018.1.0b1, 2017.3.0p1, 2017.3.0f2, 2017.3.0b1
Did not reproduce on: 2017.2.1p1

Workarounds:
Switch the hierarchy order of the "RedBox" and "BlueBox"
GameObject "Number" is disabled
"SetParent()" call in "ReparentObjectcs" script is moved before setting the "anchorMin" and "anchorMax"

Note:
Only reproduces if "TextMeshPro" is included in the project