Fly mode works incorrectly with resized viewport

Steps to reproduce:

• Create a 3D project
• In 3D View, select 2Vertical mode from "Show viewport modes"
• Resize viewport on the left to be wider, leaving right viewport narrow
• Start fly mode in the left viewport, pressing down right mouse button in area near the right viewport
• -> Sizes of the viewports reset and fly mode is activated on the right viewport
• Please see attached recording