HP 42S - wobbly "+" key

[reach]

Hi,
I stopped using my beloved 42S because the "+" key works pretty unreleable. The developer of the fanrtastic "Free42" Android app told me that there is a fair chance to fix this and that this forum should have good tips for doing this.

I did use the search function but no hits, maybe I used the wrong words. Anyway, is there really somebody who could help me? I found one video online that shows that opening it has some irreversible impact (rivets no longer holding it together). But I assume opening it is the only way to clean it, right?

Thanks,
reach