@Wayfarer another couple of tips for when you cannot resist conquering the twin needle twisting top threads issue -
1. Threading the machine - Make sure that one thread comes off the reel clockwise and the other anti-clockwise.
2. Tension Unit - If your machine has a separator in between the outer discs that clamp together, make sure the threads are laid either side of the separator in the tension unit. (If yours doesn't have a separator, pass both threads through the tension unit at the same time so they seat at the same level. )
3.
Quite important - if the threading guide at the needle clamp has two sides, use the left for the left needle and the other side for the right needle. If you have only one side to the guide, then pass the left needle thread through the guide and skip that guide for the right hand needle thread.
Hope something works for you.