What's really funny is that we are talking about 40 yr old hardware... here's an example.
I had a 800 in storage. When I put it in storage, all keys on keyboard worked. When I took it out of storage in 2021, none of the keys worked.
In 2022, I Took the Mitsumi keyboard apart and cleaned it well. This got 75% of the keys working.
I advertised it for sale at a reduced price with a faulty keyboard.
It finally sold in 2023... when I prepped it for shipping, I tested the keys again and 100% of them worked!!!!
Between 2022 (75% working) and 2023 (100% working) nothing had changed except the humidity and the date/time.
The point is... with this old hardware we are talking about, anything is possible... tread softly.