Import a MXF file (issue)

UPDATE: I'm facing another issue regarding HDR. I decided to make a little test between two workflows:

1) Original file (h.264) as the main file (h.264 HDR movie rip I made a while ago), made some cuts with a DNxHR HQX 10 bits 720p proxy, and exported directly from the source file to an h.264, main 10, level 5.1, cbr, UHD video file, with all the necessary HDR settings enabled.

2) Transcoded the original h.264 file to a DNxHR 444 10 bits UHD video file using FFmpeg, used that one as the main file, and worked with DNxHR HQX 10 bits 720p proxy. The same as before as settings for exporting. So the only difference between the two tests was the main file used as source for exporting.

The exported file from the first workflow looks good, but the second one looks very washed out. The source file in the second case was almost a lossless transcoded file from the original (used DNxHR 444, same bit depth) and the rest of the settings were all the same, so I don't know what's happening. Then I opened both "source files" (the original h.264 file, and the DNxHR 444 file) on VLC, and found out that the colors on the second one were washed out too. So the problem was, for a reason I don't know, the encoding from the original file to the DNxHR 444 one.

I know that it's always better to avoid innecessary transcoding steps, so I should go with the first workflow, work with DNxHR proxies and export directly from the source file, but since I'm learning I wanted to know why the DNxHR file looks that way. Both the source file and the DNxHR 444 file are 10 bits, UHD, same frame rate and CBR, all of that checked with Mediainfo. The only difference would be the chroma subsampling, since the source file is 4:2:0 and the DNxHR 444 file is, well, 4:4:4 (I don't think it should make such a difference in colors, though).
The other thing is that there's a very little sync issue between the h.264 and the DNxHR proxy (less than a second, I guess it's because the h.264 is a compressed file). I think I can live with that, but it will make the workflow a little harder for me because I usually edit making a lot of cuts, and some of them need to be very precise. In other words, and since I don't have a problem with having large file sizes, I would prefer working with a DNxHR 444 file as the main file, because that one doesn't have the slightest sync issue with the HQX proxy, so when I make the final export I won't have a video with extra frames that I don't want, or missing frames that I did want. That would be a little frustrating, since encoding times usually take several hours, and only then I would know about those extra or missing frames, and after that I will have to correct them and export again.

Thanks again.

Any ideas?

Thanks