Intermittent computer lock-up when suspending Dell XPS13 9360

I am running Kubuntu 18.04, fully updated with the 5.0 kernel, on a Dell XPS13 9360. I tend to put the laptop to sleep by closing the lid when not using it. It will also automatically sleep after 10 idle minutes when on battery. Basically the default Plasma power settings.

Mostly the laptop will sleep and resume no problem, but fairly frequently (perhaps once every couple of days) it will freeze with a blank screen (sometimes with just the pointer visible) and the power light on. This can happen when sleeping after being idle for 10 minutes, or when the lid is closed. Also sometimes it will not sleep when the lid is closed, meaning when I later open the lid the laptop still responds but has a drained battery.

I can trigger this manually by selecting 'suspend from the KDE 'leave' menu. This resulted in a blank screen with just the cursor displayed and the whole machine locked-up. So this is fairly reliably reproducible.

I have installed kernel 5.3-rc6 and initial tests are proving positive. I have just done about 15 suspends in a row. No lockups and the majority of the suspends resulted in a suspended laptop. A few however - say every 4-5 attempts - resulted in the laptop just going straight back to the lock screen, almost as if it had suspended and immediately resumed again. So it looks like my immediate problem (i.e. the lock-ups) have been solved. Can this be investigate however in the 5.0.0.25 kernel?

Thanks
Nick

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-5.0.0-25-generic 5.0.0-25.26~18.04.1
ProcVersionSignature: Ubuntu 5.0.0-25.26~18.04.1-generic 5.0.18
Uname: Linux 5.0.0-25-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.7
Architecture: amd64
CurrentDesktop: KDE
Date: Thu Aug 29 10:00:53 2019
InstallationDate: Installed on 2019-08-22 (6 days ago)
InstallationMedia: Kubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
SourcePackage: linux-signed-hwe
UpgradeStatus: No upgrade log present (probably fresh install)