Completed adventure-board task shouldn’t have an arrow

Device:
iPhone 12 mini

Screenshot:

Steps:

  1. Complete an adventure board special task such as “kill 150 yellow troops” (these only appear occasionally)
  2. Return to the adventure board
  3. Look at the aforementioned task

Result:
There’s still a green arrow, as if indicating that there’s something more for me to do in order to collect the gems. Clicking the arrow takes me to a suggested kingdom for finding yellow enemies.

Expected:
The green arrow should be gone now that I have completed the task.

Funny, this does not seem to occur on the more-common “Kill 100 enemies” daily adventure quota…