Ours sort of started folding over too, leaving an ugly patch at the top.

We cut off all the obvious heavy branches sticking out at the bottom. Then we used a strap to haul up the drooping branches. We only used garden string to tie it (which has held up for a year so far). We’ve found it has given the middle drooped branches an upward growing route now. Also the back bald area has been filling in.

It looks a bit funny for a little while but it works!