To reproduce:

1. Open the attached project (Bugtest.zip)
2. Open the Test -> EditorWindowTest window
3. Observe that elements of array0 are visible, but elements of array1 and array2 are not

Expected: the array elemens of all arrays are visible when they are put in the horizontal group

Fixed in: 2019.1.0a3

Reproduced in 2018.2.0a2, 2018.2.2f1, 2018.2.3f1, 2018.3.0a8
Did not reproduce in 2018.1.9f1, 2018.2.0a1
Regression introduced in 2018.2.0a2

Note : This issue is fixed on unity version 2019.1.0a3 & later.