Checkbox's test hangs when using the Back button

Running Checkbox from Ubuntu 16.04 live USB.
Checkbox's current test hangs when I accidentally or purposefully click the back button.
I need to close Checkbox and run it again to make that test working.

Steps to reproduce:
1. run checkbox
2. continue to any test that requires user interaction
3. run the test
4. click the "back" button before the test ends
5. the current test will hang

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: checkbox-converged 1.2.4-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CasperVersion: 1.376
CurrentDesktop: Unity
Date: Tue Jun 21 17:18:07 2016
LiveMediaBuild: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=pl_PL.UTF-8
 SHELL=/bin/bash
SourcePackage: checkbox
UpgradeStatus: No upgrade log present (probably fresh install)