Panasonic may not have reached the MiniDisc upper echelon like Sony and Sharp, but they did put out some fun models like their speaker dock ones (marketed as "Dockin'style MD" which started with the SJ-MJ50.
Here, we'll look at the very similar SJ-MJ55 (late 2002) which was only working with an AA sidecar. Cleaning the battery terminals (which were actually pretty clean) didn't fix the issue with gumstick battery connectivity, so we had to try something else.
In this case, we tested with a piece of copper tape to see if it could help with the electrical connectivity and it did! Once your test is confirmed, you can use adhesive-backed copper tape or find a piece of spare copper from a different donor device.
Since that electrical issue was resolved, and with this device being more than 20 years old, I decided to also open the front lid to clean/lube it.
These speaker dock models are fun, even if their speakers aren't the best. I still haven't gotten my hands on a combination of a working SJ-MJ57/58/59 and speaker dock, but I'll keep looking. I'd also love to get one of their late model SJ-MJ500s with speaker dock!