When you toggle on ortho mode using the F8 key you notice that AutoCAD either freezes or takes long to respond. But if you use the icon in the task bar to toggle on the option it responds immediately.
We have found this to be an issue with AutoCAD products on a Windows 10 operating system. It seems to be the Windows 10 Anniversary update is cause of this issue. To resolve, simply adjust your TEMPOVERRIDES system variable to 0. But be aware that by adjusting this value you will be disabling the option of using your SHIFT key to temporarily enter into ortho mode should you not have ortho mode toggled on.
This is a Microsoft issue and it should be noted that this is only a "band-aid" until another Microsoft update resolves this issue.