I'm enclosing a wiki table that sorts incorrectly when you click the heading to sort the values. The results come out like the following. Notice that identical values (zeroes) aren't even kept together.
0 X 0 0 1 1 1 9
Here is the table in wikitext:
{| class="sortable"
|-
! Bug
|-
| 1
|-
| 1
|-
| 1
|-
| 0
|-
| 9
|-
| X
|-
| 0
|-
| 0
|}This is in MediaWiki 1.28.0.