This is just an observation, but it puzzled me for a minute.
When I created this account this morning, I chose a password. As is often the case, it was quite long ( > 16 characters ).
Later on, I then attempted to sign in again and couldn't! After resetting my password a couple of times I noticed that when choosing a password, the input field has a maximum length of 15 characters. This is not the case when logging in.
Those truncated characters where causing me to incorrectly enter my password!