Lubuntu 20.04 changing screen positions then drag pcmanfm-qt and it crashes

Lubuntu 20.04 daily testing on hp dc7700 (c2d-e6320, 5gb, nvidia quadro nvs 290)

Exploration for other bugs, which involved numerous changes of screen positions (relative to one another using Monitor.Settings). On selecting a position (changed) to test I tried to drag pcmanfm-qt window so it was fully on a display (it was partially on both displays and partially off-screens).

Expected result:

pcmanfm-qt would complete window move & could be dropped on new location fully visible.

Actual result:

as I click on top window-dressing to drag it so fully on one display, window closes with entry in /var/crash showing crash.

lubuntu@lubuntu:/var/crash$ ls -la
total 20480
drwxrwxrwt 2 root root 4096 Dec 10 02:34 .
drwxr-xr-x 1 root root 120 Dec 9 16:36 ..
-rw-r----- 1 lubuntu whoopsie 20962489 Dec 10 02:33 _usr_bin_pcmanfm-qt.999.crash
-rw-rw-r-- 1 lubuntu lubuntu 0 Dec 10 02:33 _usr_bin_pcmanfm-qt.999.upload
-rw------- 1 whoopsie whoopsie 37 Dec 10 02:34 _usr_bin_pcmanfm-qt.999.uploaded

lubuntu@lubuntu:/var/crash$ sudo cat _usr_bin_pcmanfm-qt.999.uploaded
8604d884-1af5-11ea-a8db-fa163e6cac46

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: pcmanfm-qt 0.14.1-0ubuntu2
ProcVersionSignature: Ubuntu 5.3.0-24.26-generic 5.3.10
Uname: Linux 5.3.0-24-generic x86_64
ApportVersion: 2.20.11-0ubuntu13
Architecture: amd64
CasperVersion: 1.434
CurrentDesktop: LXQt
Date: Tue Dec 10 02:41:24 2019
LiveMediaBuild: Lubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20191209)
SourcePackage: pcmanfm-qt
UpgradeStatus: No upgrade log present (probably fresh install)