I'm seeing a similar error to what is described in https://bugzilla.redhat.com/show_bug.cgi?id=470740
Essentially, I have to enter my password 3 times on boot before my encrypted partitions unlock and I can boot, using graphical entry.
If I hit Esc and enter at the text console, it seems to work on the first attempt (most of the time).
I have 3 encrypted partitions (/, /home, swap), but these don't seem to correspond to the number of times I have to enter. In other words, the behavior does not appear to be unlocking one partition at a time. After the first entry, it pauses a second, as if I've entered incorrectly (even though I haven't), and then the second entry errors out and resets the input field instantaneously, as if no attempt was made to unlock the drives. Then, the third entry works normally.
This is a recent issue for me, as I've had the same setup working across several of the last few Fedora releases. I've only seen this issue after upgrading to F26, and even then, it only appeared after some update (not sure when).
Does anybody have any suggestions on how to further troubleshoot this, or have any ideas why this is happening? Perhaps a more recent bug report which matches?
Any help would be appreciated, as this is quite annoying.