Just looked at mine and it appears that you must have a pin pointing up to attach
to the hole in the bottom of the fork, right?
So everything worked just fine before you lowered it?
If the pins on your stand are not long enough I could see it slipping off,
but like everyone else said, lowering it should have had no effect.
How much did you lower it?
Here is a picture - so everyone that doesn't know what we are talking about can
see what we are talking about.
The more I look at my stand I believe it might be slightly bent
Sorry - I couldn't tell from the picture he posted.
So what holds it in place?