What can I do about Open Practice Session Freezing issues?

Navigate to your My Documents/iRacing folder and edit your Renderer.ini file.

Set the following option:

LoadTexturesWhenDriving=0 ; 0=only load when out of car

Set to 0 to disable opponent car texture loading while on track during open practice sessions, then the textures for new drivers will load only while you are out of car, and will appear white until loaded.