Html game keyboard input not working

i,
I’ve created a very simple game (top down space shooter style) which works perfectly in the Editor and when Launched to Chrome. However, when I package the game and run via the localhost server the keyboard input doesn’t work correctly.

I’m using Axis Mapping to get the arrow keys (up, down, left, right) as inputs to the game where up/down and left/right produce values of +1/-1 respectively - all of this works great in Editor and Launched games, but when I package the controlled actor keeps moving when the key has been released.
I’ve set up a print string to check the axis values in-game (when packaged) and they are not correct.

Can anyone offer any suggestions as to what might be causing this?
Thanks