"nevermind. i think i figured it out.  the manual says that in FBWA altitude is controlled by throttle amount.  ok.  i'll give that a shot."

"same thing happened to me, so I went into the arduplane basic trim page? and turned minimum throttle to zero.

i have no idea what the rammifications of doing this might be down the road.  I do know that when i switch to RTH it does come back.  but…"