I have tested this for long time. It is mystery for me. Yes ... it is a bug. I tested many landers in different configuations, diferent build sequence, diferent pre-landing procedures,
diferent approach geometry, diferent planets/moons, restarts/reboots ...
.... and ...
I have ONE ship which works ... and all its next-to-kin modifications actually do open gear (the landing code works OK),
however
if I build THE SAME ship again from begining.(20x).. those (all) fail to open gear on autoland.
It looks like MECHJEB doesnt see the landing gear.
.......................................................................
In addition - Yes ... my MECHJEB also have sometimes "stupid idaes" to fly away or miss the picked target by faaaar