system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Why don’t the members of Dumbledore’s Army have massive wand issues after learning Expelliarmus?

In the later books it’s explained that once disarmed a wizard’s wand loses its allegiance to it’s bearer. This point is huge in Half-Blood Prince and Deathly Hallows, other than simple writing flaws why would this not be a problem earlier in the series?
gpt
Aside from the elder wand, a wand doesn't always change its allegiance after it's wizard is defeated/disarmed.   The elder wand is a special case in that it values strength above all and so will change allegiance whenever it's wielder is beaten.