Missing sheep are the worst, only 5 squirrel hides. I try not to visit a village with sheep if I have a quest due, I use markers to keep track of what animals and items the villages have.
Have you succeeded at it recently?
Aaro has 100 tracking. But it's not just Aaro, I have ten active characters and several of them have had this problem. Mikko is 13 days into the quest with 86 tracking, but I tried something different with him (tracking on the zoomed out map instead of fully in the zoomed in map), and Väiski also failed it recently with 100 tracking.
Of my currently living characters:
Aaro did complete it successfully 391 days ago, by the QST file that was May 25th of this year. Aaro's currently quest was assigned on September 18th.
Egel last successfully completed it 913 days ago, assigned February 5, 2023, hasn't spawned the quest again.
Kari has failed it twice, assigned Sept 15, and May 20 2023
Mikko failed it, assigned July 13th this year
Orddotfishes succeed, assigned March 29th this year
Reko succeeded twice, assigned July 15th this year, February 23, 2023
Väiski succeeded in January 3 2024, and failed on September 17th.
Yrkki failed, assigned Nov 5 2021.
Reko succeeding with the one assigned this July makes me think maybe I am wrong about it being a bug, because that would have been in 3.84 but I've failed it 5 times since then -- Aaro, Mikko twice, Reko, Väiski, which seems really excessive.