Morning,
I had unstable lie with my second child, who is now 7 weeks. He was oblique for much of the pregnancy, wedged down by my hip, and at 37 weeks I was sent by my midwife for a scan and doctors advice on whether to admit in case of prolapse.
The baby moved while I was sitting waiting for a scan, I felt him move into my pelvis (maybe uncomfortable metal hospital chairs are good for something), and his scan presentation was therefore ok, and no further intervention was required.
He definitely shifted back between oblique and cephalic then for about another week and a half, and I went back for another presention scan, where he was (amazingly) head down. He came at 39 weeks in a good position.
I was worried about prolapse, and did all the 'right' things to help positioning; I walked, sat on the ball, got on all fours, and didn't lie or lean back. Night time seemed to be the time where he'd shift back to oblique, usually while I was asleep. It was stressful. He was a perfectly average sized baby btw, and I wasn't terribly big, so I'm not sure where he got all the space to move from.
I knew what to do in case of labour starting (for prolapse risk), and I live very near a hospital. In the event, my waters did break first, but head was engaged by then.
I read a lot about ECV, and was pretty sure I didn't want it, but I didn't want other birth interventions either... I think I might have tried it, given that he only had a few degrees to turn, but I was definitely scared about it.
Good luck, I hope your baby shifts into position soon. There's still time!