VIM cannot update file on SMB share

[Peter]

I cannot edit files on a Windows share that is smb-mounted by Ubuntu using VI, VIM or GVIM.

Other applications on Ubuntu do not have this problem, including GEDIT and LibreOffice

Bizarrely I can create a file with VI, VIM and GVIM, but saving changes in any subsequent edit session fails with:
E212: Cannot open file for writing

I attach a screenshot of the problem showing the error when I am in the mounted directory:
/run/user/1000/gvfs/smb-share:server=jcpr-dell-3,share=e/temp/uplay

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: vim-gtk3 2:8.1.2269-1ubuntu5
ProcVersionSignature: Ubuntu 5.8.0-44.50~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-44-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Fri Mar 5 10:19:47 2021
ExecutablePath: /usr/bin/vim.gtk3
InstallationDate: Installed on 2020-11-11 (113 days ago)
InstallationMedia: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: vim
UpgradeStatus: No upgrade log present (probably fresh install)