Just noticed this yesterday with my MTR-3B.
Typically, I used it with straight key mode with no apparant issues, but yesterday I hooked up a Te Ne Ke key to it for the first time and noticed that the MTR does work well with the DAH/DIT sides on the 20m and 30m bands, however…when switching to the 40m band, the DAH side now keys an “A”, and the DIT side keys an “N”. Not a DAH/DIT like the other bands did. Switching back to the 20m/30m bands, the paddle works fine. I’ve tested other paddles with this as well, same issue.
The only usuable way to use the TeNeKe is by using it in straight key mode on 40m. Is there something in the settings I may have changed somehow? Is there a way to factory reset this for troubleshooting? Any ideas?