Started update-manager from a terminal and selected merely Software Updater, clicked 'Install now'.
The installation completeed successfully and the view was automatically recalculated. The application didn't crash (no tracebacks in the terminal window) and 'apt policy update-manager' does report .23 is installed.
In Xenial 16.0.7 virtual machine, apt install --dry-run --verbose-versions correctly reports update-manager .17 -> .23.
Started update-manager from a terminal and selected merely Software Updater, clicked 'Install now'.
The installation completeed successfully and the view was automatically recalculated. The application didn't crash (no tracebacks in the terminal window) and 'apt policy update-manager' does report .23 is installed.