I found a “fix” for this on the internet, but I don’t recall where; I didn’t keep the link, but I remember what to do.
1. Remove top cover from the chassis/box.
2. Cut four strips of black electrical tape and tape it over the the outside borders of the LCD but don’t cover the LCD too far such that the electrical tape obscures the text/numbers in the four lines display. You may have to fiddle with this a bit. I did, but I got it to work nicely!
The electrical tape keeps the blue light behind the LCD from spilling over the edges of the LCD and obscuring the already dark text/numbers of the four lines display. So try this and see if it works for you. It did the trick for my MTR-5B. Oh BTW, the MTR-4B doesn’t have this problem. I just bought one of these puppies (yes, I’m a QRP rig collector it would seem) and it’s pretty good–i.e., the display is clear and it sounds great on receive and transmit.
73 de Jim, AE5ZX