What I'd expect to see here is that the object you're moving with the transform tool should snap to a position with the horizontal and vertical guides going through the middle of the object you're moving.
Try this as a quick test:
Create a new painting
Drag a horizontal and vertical guide on to your canvas, creating an intersection.
Open the layout panel via the grid button on the top menu bar, then the guides tab.
Make sure that guide snap is enabled. The default snap distance is 6 pixels, change it to 10 pixels for this test as that's a bit less subtle.
Using the oil paint tool, place a circular area of paint down on the canvas.
Select the transform tool and click the area of paint which should activate transform mode
Drag the area of paint to the guide intersection.
As the transform area moves over the intersection, it should snap to the horizontal and vertical guides when you're close enough.
The result should be that the horizontal and vertical guides cut through the central handles for the sides of the transform area.
If this works, it may relate to something specific about your original painting. If you can email me at
[email protected] and share the painting file with me I should be able to take a look at it and see what's happening.