"netplan apply" does not apply changes to netmask when CIDR notation modified on static IP

So, somebody who hadn't had enough coffee one morning typoed the CIDR notation in /etc/netplan/01-netcfg.yaml on their server, resulting in the wrong netmask for the static IP. I corrected the CIDR notation, but "netplan apply" would not pick up the new info and update the netmask. Tested across four servers running 18.04 and same behavior occurred; required a reboot to get them to pick up the changed netmask info.

Thanks!
-Suzanne