Turn the steering wheel *fully* to the left.
Then turn the wheel fully to the right and count the exact numer of turns to do this.
Then turn exactly half that number of turns back towards the left.
Then get out and look at your front wheels.
If they are not exactly pointing straight ahead, you have a toe-out-on-turn misadjustment (usually caused by setting toe when the rack is not exactly centered). This can cause kickback problems.
The other problem could be caster, but since caster is not easily adjustable in a Spridget, this means bent parts, bent frame or misassembly.
The ball ends at the end of each rack (the "inner tie rod ends") are not too tight...are they?