Hi javier,
sorry, you’re right - it’S “merge”. But since it’s “false” it’s not that.
I opened the image you sent in RawTherapee. I have to say I’m not surprised - the chair is basically unicolor. Big no-no for photogrammetry. No features whatsoever. You need to process the images so that the texture on the chair is actually visible in the images - I tried a bit and it might be possible.
What about the office chair though?