Mate-screensaver won't run slideshow. Gives blank screen

Sideshow operates perfectly in the preview window, but when it kicks in after several minutes (whatever I have set) it fades to a blankscreen. Slideshow never runs

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: mate-screensaver 1.24.0-1
ProcVersionSignature: Ubuntu 5.4.0-45.49-generic 5.4.55
Uname: Linux 5.4.0-45-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.8
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: MATE
Date: Fri Aug 28 20:53:36 2020
InstallationDate: Installed on 2020-08-25 (3 days ago)
InstallationMedia: Ubuntu-MATE 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
ProcEnviron:
 LANGUAGE=en_CA:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: mate-screensaver
UpgradeStatus: No upgrade log present (probably fresh install)