You’re having graphics issues in Inventor, but you’re not sure if it’s the graphics card or some other problem.
Go to Tools tab > Application Options > Hardware tab, and select the setting to use the Software Graphics. Then close and re-open the file to let Inventor.
This setting uses Inventor to render the onscreen graphics and therefore any graphics anomalies that exist while using this setting can be attributed to something other than the graphics card. If the issue returns when you set the option back to the recommended setting, then you should look into updating or rolling back your graphics card driver, or getting a different graphics card that handles Inventor graphic better.
Keep in mind this is a just a test, and it is not recommended to run Inventor all of the time using the Software setting, as it will cause Inventor to run slowly.