The Player's Handbook's weight descriptions for Half-Elves are inconsistent. The Half-Elf section in Chapter 2 (pg. 38) says:
They range from under 5 feet to about 6 feet tall, and from 100 to 180 pounds, with men only slightly taller and heavier than women.
However, the "Height and Weight Range" table in Chapter 4 (pg. 121) gives a weight formula for Half-Elves of 110 + (2d8) x (2d4), which is 114 to 238 pounds.
This is very different.
Do we have any reason to label one description Correct and the other A Mistake? The 2018 PHB Errata are silent on this point.
Looking at the rest of the table's formulas, Humans are 114 to 270 lbs, whereas Wood Elves are 102 to 180 lbs and High Elves are 92 to 170 lbs. (I've excluded the Drow because they're significantly shorter.)
So are Half-Elves supposed to have a slender build like Elves (100-180 lbs), or are they supposed to have a build that's intermediate between Human and Elf (114-238 lbs)?
[As a side note, changing the Half-Elves' weight modifier in the table from its current 2d4 (which is like a Human's) to only 1d4 (like the Wood and High Elves') would yield a calculated range of 112 to 176 pounds.]
One possible avenue to explore: I'm only familiar with 5e, but maybe one or more of the older versions of D&D can bring some clarity about the creators' intent.