Issue:
The normal expected functionality with logging in to the sandbox app is broken.
Test 1
Try logging in with username=alice and password=monkey1. Does this work as it did before you made changes?
Test 2
Try logging in with username=bob and password=password. Then try logging out. Does this work as it did before you made changes?
Test 3
Try logging in with username=alice and password=monkey1. Then try logging out. Does this work as it did before you made changes? Did you solve for this specific case or the general case?