On a flat world on 15w31c I tired to create a End Portal around 5 times and it is not working. Earlier on 15w31b it had worked.
MC-84815
End Portal Not Being Created
Resolved
Duplicate
0
Max Case
(Unassigned)
Unconfirmed
Minecraft 15w31c
Retrieved
Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-3461. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.