After certain troubles with Android 5 (see How to fix file permissions on Android 5 so that a certain app can access certain files?) I decided to go back to 4.4.4 on my Nexus 4 for the time being. Thereto, I restored a backup I made prior to upgrading using the TWRP 2.8.2 restore function. The restore in itself went well, and after reboot the familiar 4.4.4 boot animation came up.
But when I entered my encryption password, I immediately (no discernible delay) got a "Try Again" message. I retried several times, but my password wasn't accepted. It was definitely the correct password I entered, for in TWRP, it works.
I now restored Android 5 from a backup I made immediately before restoring Android 4.4.4, and my password is accepted again, but of course the Android 5 problems are back as well.
So: how do I properly downgrade to 4.4.4 on my encrypted Nexus 4? Thanks.