NM editor doesn't edit network details

[Uqbar]

1. Open NM plasma editor widget
2. Edit a network connection (mine is wired ethernet connection) not in use
3. Click on IPv4
4. Select "Method: Automatic (Only addresses) (was Automatic)
5. Fill a DNS entry (just one) in (I used Google's 8.8.4.4)
6. Select "IPv4 is required for this connection"
7. Click on "OK"

Expected behavior: The connection is edited

Actual behavior: a small dialog box pops up near the system tray widget saying:

Failed to update connection Wired Ethernet
connection.gateway-ping-timeout: can not set
property: value "32818144" of type 'guint' is invalid or
out of range for property 'gateway-ping-timeout' of
type 'guint'

Hint.
It looks like it's random. Sometimes step #6 seems not to be relevant. Some other times it is.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: plasma-nm 4:5.5.5-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-21.37-lowlatency 4.4.6
Uname: Linux 4.4.0-21-lowlatency x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: KDE
Date: Tue May 3 22:00:47 2016
InstallationDate: Installed on 2016-04-22 (11 days ago)
InstallationMedia: Kubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: plasma-nm
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Jochen Gruse (lpnet)]

This seems to be a duplicate of bug #1569674, which already has a reference to an upstream bug fix.
Jochen