This problem still exists for villagers that were traded with during the 39w snapshots. Tested in single player survival 1.7.2
I have fallen into lava 5 times because of this glitch. It is especially a problem when dismounting to let a horse go through a portal in the nether. Even if the portal in enclosed in a room made of cobblestone (2X4X3 inside dimensions with 3 walls) when dismounting it is common to be booted out of it and to fall into lava.
Was not able to reproduce in 1.16 Release Candidate 1.
After ~1.5h in creative at a naturally generated village placing 543 lectures and tabulating 366 enchantments in excel, I finally got Unbreaking III.
The only enchantments I did not get after 366 measurements were: Bane of Arthropods I, IV, Fire Protection I, III, Protection III, and Sharpness I, but due to the "small" sample size this time, their absences aren't statistically significant.
It could have been resolved, or it could be that I was just incredibly unlucky before.
Tangent: have I mentioned that the enchantment system is too cluttered in vanilla? Why do both Flame and Fire Aspect have to exist? Why are bow and crossbow enchantments separate? Why does Bane of Arthropods exist? For that matter why Impaling?