Cross/Analog keys toggled with LShift/LAlt combination

[movomo]

Hello, first off, thanks for this super performance psp emulator.
I have a question regarding L-Shift and L-Alt key combinations.

I'm trying to set up Monster Hunter 2nd G (running JP version), imitating Monster Hunter Frontier Online's (PC version) keyboard controls. The problem is, if I hold down the LShift key and input analog keys, cross key(s) of the corresponding analog direction is toggled on (stuck) and left pressed until I hit the cross key.

So... I discoverted these things
- L-Shift toggles cross keys when analogs are pressed down. Doesn't do anything when pressed with cross keys.
- L-Alt toggles cross keys when cross keys are pressed, toggles analog keys when analog keys are pressed.

This LShift is key is kind of crucial to my keyboard setting. Is this a keyboard hardware issue, or PPSSPP feature? If this is an intended feature, is there any way to change this behavior? - so that I can send the toggle keys away to somewhere I'll never hit?