Sounds like the problem I had, I thought the shoes were worn but on
investigating I found a washer was missing which fitted between the
upper casing and the brake shaft. I found a suitable one in my
collection that gave the desired action. IIRC it was about 0.080" but
don't quote me on that.

Grant Erwin wrote:

On both my J-heads, the spindle brake acts just the same. Push it
forwards or pull it back and it engages the brake, everything feels
fine. In the manual, however, it says you can push/pull it and then
lift it up and it will engage the lock mechanism, but on neither of
mine does this happen.

Is there an adjustment I can make, or are my brakes worn out or
something?

GWE