For some reason in this game I cannot run in a diagonal direction.

The mappings for this game are for P1 to use the keypad, as in UDLR = 8246

The players will only run in the 4 cardinal directions, and not diagonally. If I press the diagonal keys on the keypad (7913) they will run diagonally, but not if I do a combined press of say buttons 8 and 6 to run to the upper right.

I've tried with both NUMLOCK on and off with the same result.

I tried the mapper (CTRL+F1) and mapped the 8246 keys to the arrow keys, but that also will not allow them to run diagonally.

Can anyone assist?

Thanks in advance