I am looking at https://he.m.wikipedia.org/wiki/User:Mikey641 (the mobile user page for User:Mikey641 on the Hebrew Wikipedia).
Under the title it says: "הצטרף לפני 2 שנים" ("joined 2 years ago"). The wrong plural form is shown here. For number 2, the output is supposed to be "הצטרף לפני שנתיים".
The PLURAL clause in the translation is "{{PLURAL:$1|שנה|שנתיים|$2 שנה|$2 שנים}}", and I'm pretty that it's correct. In case it's hard to read it right to left, I'll break it down:
1: שנה
2: שנתיים
3: $2 שנה
4: $2 שנים
The translation that I actually see is 4, which is the "other" generic plural. I expect to see 2, which is the "two" form (dual).
I also tested it at https://he.wikipedia.org/wiki/User:Amire80/2 , and it looks correct, but it's parsed in PHP.
(Sorry about possible over-tagging, I'm not sure where the issue is.)