Checkerboard background player

Hello All!  Recently discovered a handy (or what I thought was a handy) little setting in FCPX.  In "settings" under "playback", you can choose to change the color of the player background from Black, white, or checkerboard.  I had no idea of this setting, and considering I have switched to using open frame (4x3) for a lot of my shooting now, its sure handy to know if I haven't changed the shot to 16x9 when I am editing.

But here's the problem I can't figure out:
at first, every clip in the timeline shows the checkerboard background when I throw it in the timeline.  But I have quickly noticed as soon as FCPX has finished rendering that particular clip (and every other clip in the timeline), the checkerboard player background goes away and is replaced with the black player background.  I can even scrub through my timeline, and the checkerboard player background will disappear and re-appear based on whether or not that section of the timeline has been rendered.

For me, this sorta defeats the whole point of having the option in the first place, my M1 Mac is quite fast at rendering and after putting a clip in the timeline, I may not get back to it for several minutes, at which time its already rendered in the timeline and the checkerboard background player has disappeared.  Anyone have any thoughts on this?

Switch off background rendering and delete the render files. Don’t render. You could also set ProRes 4444 as the tender codec, but that will create huge files.

I have a similar problem. I cannot get the checkerboard (or the white) backgroung to show at all. I did get it briefly by creating a new library and new project with one still clip, but the moment I clicked play, the background became black and I could not, no matter what it did (deleting the cache, the generated render files, and the plists) get it to return in that library or any other. Final Cut (10.5.6) running on OS 11.7.4 (Big Sur)
Any suggestions?

You mean 10.5.4? Unfortunately that was a problem in that version with the first clip in the timeline. You might be able to cheat it by putting a blank clip or a blank title in front of it.

Sorry, I mean Final Cut 10.6.5 

I haven't seen that problem in this version. Perhaps it depends on the media format and resolution and project properties. You might try the gap clip or blank title before the still.

P.S. Make sure background rendering is switched off or the render codec is set to ProRes 4444. 

Creating a new Library and Project and beginning that project with a gap clip worked. Many thanks.

Once rendered, what you see is the background as it is supposed to be — the checkerboard disappears. It's been this way at least since FCPX 10.4.

I made an "adjustment layer" Title that will create a persistent checkerboard even after rendering.  You can adapt the checker sizes to anything you like and recolor it if you like. Just make sure that the Checkerboard Background adjustment layer is above everything else!! Otherwise, some media may become obscured.

The FCP preference can be left on Black. Toggle visibility by selecting the Checkerboard Background and type the V key.

"Plays well with drop shadows".

FWIW