I saw there was an issue closed for the cropping behavior here but I don't think the key problems with the cropping behavior have been fixed, namely how the box moves in a seemingly random manner, often contradicting the inputs of the user. The only way to sort of get it to work is to use 2 fingers in diagonally opposing corners, but even that's not perfect and frankly I don't think it should be necessary either.
I understand there's no standard behavior for how a crop box should work, but I think it can be much better than what it is currently.
I would like to point to the way Snapseed's crop box behaves, which is also how many other gallery crop boxes do it as well: Dragging one of the edges extends only that edge, with all the other edges remaining in place. And dragging one corner moves only that corner, with the 2 adjacent edges following behind and the diagonally opposing corner staying in place. And lastly, dragging your finger in the middle of the box moves the whole box without changing its shape.
I think implementing a system like that, or at least similar to that, would vastly improve usability. Anything that doesn't make the box move and resize all over the place when you just want to adjust one edge or one corner would already go a long way.
I mainly use this app to quickly crop things and send them, so having a properly working crop box is vital for me and I'm sure many other users.
I hope this can be addressed.