On the one hand…on the other hand

The expression 'on the one hand…on the other hand' is used when you are comparing two different facts or two opposite ways of thinking about a situation. It is used to introduce a point of view, fact, or situation, followed by another that typically contrasts with it. (B2)

It is never used to add extra information.

Besides, it is used to introduce TWO elements, no more than that (after all, you only have two hands).

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If you mean to say "Por otra parte" but what you are doing is not establishing a contrast, but rather adding information, please use any of these expressions: https://natalialzam.wordpress.com/2021/03/02/linking-words-to-add-ideas-information/

Context: https://news.sky.com/story/more-than-1bn-in-state-pensions-underpaid-due-to-repeated-human-errors-12414099

-Are things better now?

-On the one hand, the Department is taking this incredibly seriously (…) [positive argument]; on the other hand, they're still relying on the same basic system they've always had (…) [negative argument, it's the system that caused the mistakes in the first place].