Hi Ben, this doesn't have anything to do with the hardware, it's just a side effect from how MoI's zoom works in a perspective view by approaching the rotation pivot point.

When you zoom in a perspective view, what actually happens is the eye point moves forward, and MoI tries to step the eye towards the rotation pivot point without trying to go past it. When you're seeing smaller zoom amounts, that's when you're getting fairly close to the rotation pivot point.

The main thing to do in this situation is to reset the rotation pivot point to be better suited to your current object, there are 2 ways of doing that - one is to select an object and use the "Reset" button on the bottom viewport toolbar. That will zoom the window to fit the selected object and it also sets the rotation pivot point to the center of that object.

The other main way to set the rotation pivot point is to use the "Zoom area" tool in the bottom viewport toolbar - that will allow you to pick a center point and an extents box and try to fit the view inside of that - also the center point that you pick becomes the new rotation pivot point.

So for example if you're trying to zoom in to a particular corner of a box for example, do the "Area" zoom, and snap the center of the zoom window onto that corner using object snaps - that will basically set your point of interest to that spot and you will rotate around that point and also when you zoom it will step more naturally towards that particular point now.

When you're getting slow steps it really means the rotation pivot point is set somewhere too far away from the point you want to focus in on.

The other thing you can do is to turn off perspective, that's done under Options > View > 3D view projection: "Parallel". When the 3D view uses a parallel projection instead of a perspective camera, zooming works the same as it does in the Top/Front/Right viewports where it's able to directly modify a scale factor instead of just moving an eye point around.

Let me know if you are still stuck or if this explanation does not make sense.

- Michael