"Failed to start scanner: Invalid argument"

A new Epson WF-7710 installed yesterday.
Various files missing in /usr/share/sane/xsane/doc and elsewhere - linked them in succesfully.
Xsane now detects 2 devices with closely-similar names (the name note displayed fully, however)
Scan appears to start whichever device has been selected (the scanner physically starts to react), but then whichever device is selected, I get the message "Failed to start scanner: Invalid argument"
When starting from a terminal window, the following messages appear BEFORE tdhe 'Scan' button is hit:
Capability : [(null)]
Capability : [image/jpeg]
Capability : [image/jpeg]
Capability : [image/jpeg]
Capability : [image/jpeg]
Capability : [image/jpeg]

SimpleScan (Document Scanner) works without any problem.

I have tried renaming .sane/xsane and restarting xsane; but that makes no difference. The same problem appears again.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xsane 0.999-8ubuntu2
ProcVersionSignature: Ubuntu 5.4.0-53.59-generic 5.4.65
Uname: Linux 5.4.0-53-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.11
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: X-Cinnamon
Date: Thu Nov 12 12:28:50 2020
InstallationDate: Installed on 2017-03-09 (1343 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: xsane
UpgradeStatus: Upgraded to focal on 2020-09-30 (42 days ago)