spectacle has a scrambled screen when taking a rectangular region screenshot on a 4K monitor

[Matthew Darwin]

Run Spectacle
Choose Rectangular Region
Delay 2 seconds
Click "Take Screenshot"
Wait 2 seconds
the screen shows all scrambled
Try to estimate the corners of where you need to take the screenshot
Press enter
The captured image looks ok

The problem is trying to capture the image because you can't see where you're drawing the box.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: spectacle 0.25-1
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: KDE
Date: Mon May 14 19:59:43 2018
InstallationDate: Installed on 2016-05-25 (719 days ago)
InstallationMedia: Kubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
PackageArchitecture: all
SourcePackage: spectacle
UpgradeStatus: Upgraded to bionic on 2018-03-11 (64 days ago)

[Matthew Darwin (bugs-mdarwin)]

I just got a new 4K monitor. The exact same software using an older monitor worked fine.