The bug is fixed. Thanks.
During the installation, I spotted the "restore previous cfg file" button, so I clicked on that.
It's been several minutes now, and I'm still seeing the screen below. It presents conflicting information: a "please wait" notice, and an "Installation finished successfully!" notice.
There's no indication that anything is happening.
Why would it take so long to restore the previous cfg? Or is the screen presenting the wrong information? The cancel button is grayed-out, so I hit the "Close" button and it appears that TDM is using my previous cfg.