I have updated the upcoming Ubuntu 19.10 to CUPS 2.2.12 and now I cannot do quick configuration changes with cupsctl any more.
When I run

$ cupsctl --share-printers

or

$ cupsctl --no-share-printers

I cannot access CUPS any more:

$ cupsctl
cupsctl: Unable to connect to server: Bad file descriptor
$ lpstat -v
lpstat: Bad file descriptor
$ 

I have to restart the daemon to get access again. At least then the configuration change gets effective:

$ sudo systemctl restart cups
$ cupsctl
_debug_logging=1
_remote_admin=0
_remote_any=0
_share_printers=0
_user_cancel_any=1
[...]

Here are my config files and error_log (in debug mode):
cupsd.conf.txt
cups-files.conf.txt
error_log.txt