export very slow

Hi friends,
I'm trying to export a 16' project, 1920x1080p h.264 25 p.
The majority of the original footage is 4k from a Panasonic GH4 camera. Most B-rolls are from Canon 5d Mark III.
Nothing complex, just some luts apllied via Color Finale.
Well, I have tried both fcpx and compressor, but the render time is huge in both cases. After and hour and a half it has reached 30% of the render.
I have quit fcpx and now It is showing me that I need to re-render most of my timeline, something that has been done before and that took A LOT of time.
It seems like a bug. Any help appreciated.
Running fcpx 10.2.3 on El Capitan 10.11.4 on a macbook pro i7 (late 2013), 16gb ram.
Original media is on thunderbolt hard drive.

Deleting fcpx preferences has solved the issue for the moment.

Hey Pablo,

Glad to hear you have found the solution, and thank you for posting it.

Transcoding to H.264 while at the same time downsampling your footage from 4K to HD can indeed take some time, but what you were seeing was not normal. It's always a good idea to start with refreshing your FCP X preferences when you experience abnormal performance behavior.

- Ronny