If double-clicking inside a viewport causes the display inside to what is best described as Zoom>Extents, your file has a setting that needs to be changed inside each and every viewport in each and every layout in this one DWG file.
First, lock your viewport (a great habit on it's own), then double-click inside it. At the command line type UCSFOLLOW, and set it to 0 (zero). You may now safely unlock your viewport, if you must. Don't forget to repeat in every other viewport in this file.
Explore UCSFOLLOW in Help in LT and explore it's feature.