Final Cut Pro x 10.4.7 Bug: Any effect brings a blinking rectangle on the top left quarter of the image.

it only happens after export. It's not visible at any point for me in the time line. I exported the entire project to receive notes on it before going back in to make minor changes to it based on viewer feedback. After do this (and upgrading both the os and fcpx) I see this happening. It was all exporting fine before the updates. I had a tech support person on the phone and after he linked up to my screen and he saw it happen with his own eyes, he insisted that it was due to a problem with fiilmconvert. So film convert is saying it's apple and apple is saying it's film convert.

aaaaah, I extend my last question and ask if the problem is still solved with the epgu when you export H.264

because I‘ve read that in this case the egpu is not used. So maybe the flickering rectangle would reappear in that case. What‘s your experience here?

Have you solved this issue? I’m having the same issue as well using motion VFX films mLUT for application of custom LUTs. Please help!!

I am having the same problem in Catalina 10.15.1 and fcpx 10.4.7 on a mac mini 2018.

Not necessarily. The GPU gets used to render many effects together with the CPU.

No no build in fx that I've used is producing the problem. For me the problem is only on the exported file h264 and prores not in the rendered time-line.

That's worse than the LUT problem. I don't think Apple can fix this.

Well, unfortunately I used film concert to color grade the entire project which is about 97 minutes long. It would be an enormous amount of work to redo it all with a custom lut.

Thank you Rephil3!

And you had the same issue with the rectangle in the exported movie as well, which is gone now?

You are welcome, yes exactly the same.

One last question: Which egpu do you use? I have a 13‘‘ Macbook Pro (2017) and would buy the blackmagic egpu

I contacted film convert and they said to talk to apple because, "FilmConvert only modifies the image buffers provided by FCPX... it doesn't retain any image data and so I can't see how it could be causing the problem that you are seeing. 

Unfortunately you are screwed then. Same was I.

Did anybody try to use an egpu? Would that solve the problem maybe (since it seems to be an issue with the lower-end graphics cards)?