How to reproduce:
1. Open the attached project
2. Open Berserker(Ieva) scene
3. Select transition from Idle to Intro and preview the animation (all good)
4. Select one of the .FBX files from Animations folder
5. Select Rig tab in Inspector and change animation type from humanoid to generic
6. Apply changes
7. Select Animations tab, drag the same .FBX character to preview and preview the animation
8. Change animation type back from generic to humanoid and apply changes
9. Repeat step 3 and notice that it doesn't work
10. Select Berserker in hierarchy and notice the warning in the Inspector (it thinks that generic animation is still used)

Workaround: Reopen the project