re-rendering already rendered projects on re-opening

Hi, hoping someone can help me with this. It's a bit of a weird one.

Is there any reason why FCPx should re-render a project on re-opening when it finished rendering before being closed? This is happening constantly with a project I'm working on at the moment.

It is a little unusual (5760 X 1080 prores 422) for a theatrical presentation to be split across three screens, but I'm not sure why that should make a difference.

I haven't come across this issue before.

Any ideas?

Thanks in advance, David

Are you talking about background rendering?

Yes that's right Ben.

DavidL1970 wrote: ...Is there any reason why FCPx should re-render a project on re-opening when it finished rendering before being closed? This is happening constantly with a project I'm working on at the moment...

There have long been some significant issues with how effectively and reliably FCP uses cached render files. Loosing render files upon relaunch is sometimes seen, but there are many different manifestations of the problem. In general it may be partially related to certain effects, both built-in and 3rd-party. See this post which discusses whether it got any worse in 10.15.1. Read also the linked posts which give more background on the issue:  www.fcp.co/forum/4-final-cut-pro-x-fcpx/...es-for-export#111997

It is not isolated to background rendering, however you can try disabling that, deleting render cache and manually rendering the timeline as needed using SHIFT+CTRL+R. If using proxies, those have separate render cache and must be rendered separately.