I had a very similar experience with a 15g sapodilla tree I bought a few years back. It was staked for too long so it was very rubbery and thin but I removed the stake when I planted it and the entire tree bent 90 degrees about a foot off the ground. Thanks to it being so rubbery it surprisingly did not break. I staked it back up using two stakes about a foot away on adjacent sides of the trunk and tied to each and around the tree in order to encourage the tree to build up a stronger trunk over time. I removed the stakes maybe about a year later and now the tree is growing well and producing decently.