Originally Posted by
maddog34
from a reputable source, online....
2021 Trek FX4.
Headset
1-1/8'' threadless, sealed cartridge bearings
the individual bearing balls in a sealed bearing Cartridge assembly can not be "replaced" by a mechanic in a bike shop.
the entire sealed bearing must be replaced, especially when one considers that the SEALS would be bad if they allowed the bearings to rust......
sumpin' ain't right.
i'm falling back to the wrong cartridge being installed.... or it was installed upside down, maybe?
on the upside... you may have gotten a new cart. bearing for the price of ten measly balls

Thanks. You all have confimed what I thought - something wrong/weird going on here.
Regarding the missing balls - I wondered the same at the time. Where did they go? And why did they wander off? I should have asked more questions. Never having a headset apart, I guess I didn't think through all the implications.
Updates when I have them.
Mark