Affects Version/s: 22.214.171.124 Beta, 126.96.36.199 Beta
Fix Version/s: 188.8.131.52 Beta
MCPE-19700, but it's not random/inconsistent or dependent on item frames – the broken elytra texture simply never shows up at all anymore, in any context.
1. /give @p elytra 1 429
2. Equip it
3. /tp ~ ~20 ~
4. Start flying and wait for the last bit of durability to wear out, you'll fall out of the air
5. Check inventory
This is caused by the recent separation between legacy damage values, and proper durability damage for tools/armor. Elytra edited to have legacy damage 431 appears broken, where elytra with proper damage 431 does not.