Re-rendering every time I open up FCPX projects

Not posted for a bit, hopefully someone can advise

I am working on a project (actually several small 5-10 min projects.. I have background rendering on, once completed its fine..

When I close FCPX and open it up again, the projects start rendering again!!

Any ideas a s to why this is happening if I haven't changed or added anything??

PS using latest FCPX release and latest OSX Mojave

Why do you have background rendering on? I'd turn it off, wastes disk space, wastes CPU time, shouldn't be needed in most cases. This is a bug. But again, why are you keeping background rendering turned on?

good point, why do I have it on.. guess im just used to it rendering whilst I work on two machines at once

Will switch it off and see if this speeds up my process

99% of the time you don't need it. It is only there for situations when your Mac is too old or underpowered and can't give you good enough playback for editing. Turn it off, delete all your render files, be free.

Thanks, thought it was my late 2013 iMac i7 slowing down for some reason

Because Apple is dropping the ball constantly these days. Are you using native only plugins or red giant/neat etc.. as well? 10.4.4 introduced this re-rendering bug and have been going mute on the feedback forms. They used to reply once in a while, now they run on auto-pilot not fixing any bugs that show up. Report it as I have and hope for the best.