After I did an overhaul of my threaded headset, it loosens after every ride. I'm struggling to find what causes this, as I've done this job on different bikes without any problems. So far I've did the following:

• Changed the upper loose ball bearings with a cage as the balls were difficult to keep in place. I've checked that the cage is in the right positions
• Checked that the lock nut is not pressing against the fork tube; this wasn't the case.

What else could cause this behavior? See below a picture of the headset in question:  

After I did an overhaul of my threaded headset, it loosens after every ride. I'm struggling to find what causes this, as I've done this job on different bikes without any problems. So far I've done the following:

• Changed the upper loose ball bearings with a cage as the balls were difficult to keep in place. I've checked that the cage is in the right position.
• Checked that the lock nut is not pressing against the fork tube; this wasn't the case.

What else could cause this behavior? See below a picture of the headset in question: