Crash after opening and joining Tier 17 Map

Opened a Tier 17 Map for the first time to unlock the 5th Map slot.

After encountering the first mob group, the game crashed and indicated Error Connection to Server, failed to join instance.

When wanting to rejoin after being logged out (clicked on the portals), indicated:

Error: Failed to join instances because: Disconnected from Server.
Error: failed to join instances.

Then the remaining portals to the Tier 17 Map disappeared.