Steps to reproduce:
1. Open attached project
2. Open "test" scene
3. Press play
4. Click RMB and observe normal transition between default and aim states, press RMB again
5. Repeat step no. 4 while holding "A" key
6. Release "A" key and make sure you're not aiming
7. Hold "A" for 1-2 seconds
8. Quickly release "A" and at the same moment click RMB
9. Observe a very slow transition (when Animator parameters(Forward/Horizontal) are not equal zero)

Note: keep an eye on Console as it prints out transition details (it prints out normal transition time even though it is very slow)

Reproduced with: 5.3.6p2, 5.4.0p1, 5.5.0a5