Co-op Difficulty Limits

Earlier on in the month, I found out another Player could change Co-op dungeon difficulty to X, when I had only been able to change to difficulty I. I could only change skirmish to X. After realizing I had completed all Dungeons at X, except one completed at VIII, I completed that dungeon at X, and voila.

I could change Co-op to difficulty X.


Until today. Now, all Co-op skirmishes and Dungeons are limited to difficulty I, despite having completed all dungeons at X.

Just wondering why this might have happened. Is it detrimental to the game for advanced players to help newcomers to have access to more ore, gold, and food? Or is this a bug? Or was this change made as a precaution to future changes to co-op?

Bug, per Jeto. This issue has affected my account as well for a very long time. AFAIK, the issue is scheduled to be fixed in the next hotfix, 1.1.1.