Font switch back to normal size and type while rendering and restart fcpx

I have this problem so many times, when I change some titles to Bold, and render, it shows the normal font, and sometimes I have different sizes of titles in one text, and even I change titles to the same size, and delete the project and library render files, the render results back in the normal type and size. The only way I figure out is add a space at the end of the test, one by one, and I heart lots of people have that bug too

and sometimes same issue with LUT plug-in.