Motion object disappears outside project boundaries and appears as a square

Okay...

I think you are mixing and matching two different tutorials... albeit with similar concepts and constructions... but still different.

#1 Marten's tutorial:

He's using 37 drop zones arranged in a circle (one at the center). The radius of the circle for the drop zone arrangement is 20,000... units (or pixels if you like). The Camera is set at Z (position) = 20000, lined up with Drop Zone 1. ALL drop zones face forward — they are NOT rotated to match the circumference of the circle. This project does not need to be arranged in a circle — a straight line would have done just as well.

#2 Bates' tutorial

He's using a Circle shape as a Motion Path AND he rotates the drop zones to align to the circumference of the circle path. The Circle path radius is only 2160 units.

The camera is going to behave differently with the face-forward drop zones and the path-aligned drop zones. The circle aligned drop zones are going to introduce **parallax** which is that drifting left/right effect you're experiencing since the camera does not stay "face aligned" with the drop zone.

So, if your project is heavily reliant on Bates' tutorial, then you 1) really cannot use the Throw behavior, OR, 2) ignore the Point At behavior step and keep all the drop zones facing forward (Y rotation = 0). You will probably also have to increase the Circle Path radius so that the camera doesn't basically pan over the edges of the drop zone as it is leaving one framing to go to another. And, adjust the Camera's Near Plane parameter so that Drop Zones appearing to move forward after Framing will fade away quickly.