Login problems with Fedora 29

This one is a bit of a mystery...

I have a newish install of Fedora 29. I am using two SSD drives on a
Lenovo W540 laptop with UEFI boot.

Every once in a while the system stops accepting my password. Rebooting
does not help.

I can mount the drive with a live F29 distro and chroot the root drive. I
have a backup of the /etc/shadow file and there are no changes to the
user. "changing" the password fixes the problem.

I am using the Gnome 3 desktop.

Ideas why I am seeing this?

perl -pe 's/^\s+//g' *.py