Summary of the issue (title of the post)
In one village I found a "Mounted Archer" at research level 11 (eleven). But there are usually only 10 levels on the beta world.
If I am allowed to make a rough guess:
Could be that the barbarians researched it up to this level before the village was conquered?
Overview of the bug (description):
"Mounted Archer" at research level 11 (eleven). Village ID: 91160 on zz2.tribalwars.works