100% a program problem. Found key rebinds but do not understand. Keyboard is completely functional and only fails within program.
To point out again, ANY other peripherals can fuck this up if they have drift / are stuck in one direction. So make absolutely sure you don't have a controller, joystick, racing wheel, flight simulator, ecetra plugged in. You could also plug in a controller and play using that.
Also, something you might need is to restart your computer. Sometimes that's all that's needed to fix some issues. I used to have this kind of issue with an old game on a different engine (Baldur's Gate 2, on the Infinity Engine), and restarting the computer was the fix.
As for keybinds, I guess this version of RPGmaker didn't have rebinding for direction controls. Been a long time since I looked, so I didn't remember. To explain what they are, there are a set number of keys that RPGmaker will recognize, listed on the left of the columns. The drop down menu lets you select which game function will be recognized. The dropdown list is generally C = accept, B = cancel / open menu, A = dash / skip dialogue, L and R = move menus left / right (like looking at character 1's equipment, L/R will let you switch to character 2's equipment without backing out of the equipment menu). X Y Z vary depending on the game, but often include hiding dialogue boxes and standing character images on the side of the screen.