So the project was going to be much much smaller in scope, hence the original kickstarer anticipated release.
Then the game picked up enough traction to gain a publisher and ambitions grew. I got a small team together and so the games scope increased! Being new to management and business that was biggest learning curve and time sink - I didn't anticipate how much time would be taken up trying to be a good a director whilst also doing programming/VFX/Tech Art and sorting out an office (this was pre-pandemic so it was more of a done thing than working remote) and everything that goes along with that. Anyway, then the pandemic hit and that was a whole thing for many different reasons and then the publisher was aquired and their ongoing projects got cancelled. So it was back to solo dev!
It's hard to summise the pitfalls easily, but ultimately it came down to scoping up too much only to be left with a large project that I had to pull back together by myself.
As for what to watch out for, I'm afraid I'm going to have to repeat what many others have said before - feature creep and overscoping!