Linear bearings - can someone help with how to reload?

Long story short - some of the balls from my linear rail bearings
have come out. There is a hole to feed them back, but I can only get
one ball into it. Are all of the balls in a bearing like this
generally on a single track? I have the space that the balls came
out of above the hole, but the balla want to go in - not up, and I
can only insert a single ball. I tried a magnetic screwdriver, but
either gravity or the shape of the track is working against me.

Any guidance would be appreciated.

Jeff (Otherwise known as panicked)