Grand Mirror placed on Monastery of the Keepers prevents re-entry

I encountered a bug where the Grand Mirror appeared on Monastery of the Keepers.

After this happened, I was no longer able to enter the map again. When I tried to activate/traverse the map, the game displayed the following error message:

Activation failed. Waystone tier is too low for this Map.

However, the map tooltip shows that Monastery of the Keepers requires:

Waystone (Tier 6) or higher

Because of this, I cannot re-enter the map and continue the Grand Mirror encounter/progression.

The map cannot be entered, and the game displays:

Activation failed. Waystone tier is too low for this Map.

This prevents me from accessing the map and continuing the Grand Mirror encounter.