HP30b - reluctant key

[jebem]

Thank you for sharing your experiment on this machine.

While I did similar repairs on other models and brands, I didn't try to repair this specific model (not yet).

This model is well known for presenting this defect, even on "like as new" specimens.
Therefore this issue doesn't look like to be caused by the usual metal wear and oxidation resulting from prolonged usage.
I would say that early key contacts isolation is something related to poor metal resistance to oxidation combined with manufacturing contamination.

Did you by any chance took some pictures of your work that you could share here as well?