Object mask toolbox. Timeline red when having video with effect and sometime the program is freezing and only mouse is moving.

Hello ​@Stellar_Flamingo3ddf,

Welcome to the Premiere forums! We are glad to see you here. We need a few more details to help us understand the issue. Please see, How do I write a bug report? for our preferred format. Specifically your system specs and the Formats in your sequence are helpful when it comes to playback issues.

Like ​@Peru Bob I am also curious if rendering your timeline resolves the issue. Red means that playback may be impossible during that segment because there is just too much to process, so rendering it allows it to reference just one video preview during playback instead of drying to decode, process any and all effects, then encode the file in real time. 

Thanks for reaching out. I hope we can help you soon. 

Thanks,

Amy

Does it play OK if you render the timeline to turn the red to green?

Try updating or rolling back your graphics driver directly from the video card manufacturer’s site. If NVIDIA, do a clean installation of the latest Studio Driver (NOT the Game Driver).