I read an article on Fox News saying that New Mexico Senators were filing a law suit claiming some 600,000 acres in the Texas Panhandle. Being a Texan who has lived in NM, I found most of the article humorous especially the part about claiming El Paso. The article said that there were only "illiterate Mexican" shepherds as witnesses vs. Texas engineers as to how the river flowed when they were young. The article did mention that if you believed the "illiterate Mexicans", El Paso would not be New Mexico, but would be in Mexico. Maybe that is why the Senators dropped that part of the claim.
As to the Panhandle land, well, maybe the surveyors got liquored up or greedy and messed up - I do not know. But as I remember my Texas History, when Texas won their independence from Mexico, they claimed up to the headwaters of the Rio Grande. It seems to me that about half of New Mexico should belong to Texas. For whatever reason, when Texas decided to become part of the USA (1845), they gave up part of their claimed land and made the boundary(1850) as it is today leaving New Mexico as a territory until about 1912. So why did the New Mexicans wait 150 years to file suit? I know they are the "land of manana", but that is ridiculous. Something else I remember from my Texas history is a flag that the Texans flew. It had a picture of a canon that the Texans had captured from the Mexicans during their battle for freedom. The words on the flag were "Come and get it". I think that should be the words for Texans now, and a reminder to the New Mexicans.