Visual Studio, Microsoft Office, and many other applications making use of docked windows are subject to the rigors of "helpful" mouse software suites, kindly loaded by computer manufacturers. Such manufacturers include HP / Compaq, IBM / Lenovo, and others.
Turning the mouse scroll wheel causes docked windows to scroll, instead of the code or document window.
Remove third party mouse software. (For example, Lenovo Mouse Suite) Mouse drivers and utilities provided by Microsoft are more than capable of handling your pointing device needs. This excludes other software used for gaming mice that use macro software.
See related post: Mouse Scroll Wheel Issues with Visual Studio