MC-103497 was about the <DragonFight> tag inside level.dat not being saved if no player visited the end during a server session, and then being regenerated incorrectly. This is now fixed. However, worlds that were affected by the bug do not have the regenerated data corrected.
- If <ExitPortalLocation> was regenerated prior to 1.10.1, it has an incorrect <Y> value that does not correspond to the actual portal in the world.
- The <Gateways> tag when regenerated contains the entire original list of gateways, thus killing the dragon will recreate existing gateways before opening new ones.
As a workaround, both of these can be easily fixed by using an NBT editor to fix level.dat.