When I was looking up the syntax for creating a shape I came across this entry in the mohoscripting.com website:

https://mohoscripting.com/methods/82
Which if correct suggests that when creating a shape if we don't give a frame number for which frame we want to create the shape on, Moho will default to creating it on frame -1,000,000 , ie negative 1 million.
Just wondering is this the reason we are getting negative frames?