reagan_anderson
Rendering the Timeline is not a repair tool for problem video. It is a preview feature which is your window of opportunity to catch a problem sooner than later.
Any Timeline content without the orange line will not render since that render indicator is telling you that you have the best possible preview displaying in the Edit area monitor at playback of the Timeline content.
If the preview is not giving good results, there are two troubleshooting avenues to follow
1. ignore what you are seeing and move on to export to determine if what you saw on the Timeline is reflected in the export.
or
2. troubleshooting your project settings, the properties of your source media, overall Timeline content, computer resources, etc
You wrote...
Also, some of the footage that isn't rendered is fine when I play back my project - no lagging or stopping, however some other content that's not rendered lags and stops during play back
An unrendered Timeline can look fine, but is can look bad in the end product. The rendered Timeline is your way to obtain the best possible preview and be more confident of what you are going to get as end product. Specifically....what is the render indicator line when you say ".....however some other content that's not rendered lags and stops during play back?
I need to move on with you to evaluate your project settings and source media properties and storage. But, I do not want to leave the "rendering" matter until I am sure that you are OK with what I am trying to tell you about Timeline rendering.
Please review and consider.
Thank you.
ATR