KDE hangs on subsequent login

After I upgraded to Fedora 31, an unusual problem began happening. First login after boot, no problem. Logout then login again, the session hangs. The only thing on the screen is the splash image. Sometimes I can jump to another console (ctrl-alt-F2) and reboot the machine from the command-line, sometimes not, in which case I have to power-cycle the machine.

This happens with and without a network connection. I have tried it with multiple user accounts too. I have tried cleaning out KDE cache files and directories, although I don’t have an exhaustive list of everything.

My system:
Operating System: Fedora 31
KDE Plasma Version: 5.16.5
KDE Frameworks Version: 5.61.0
Qt Version: 5.12.5
Kernel Version: 5.3.8-300.fc31.x86_64
OS Type: 64-bit
Processors: 4 × Intel® Core™ i5-4590 CPU @ 3.30GHz
Memory: 7.7 GiB of RAM

Please let me know what other data to provide and any recommended troubleshooting steps.