Xsane delays to start receiving data until scan finishes

In all Ubuntu / Kubuntu versions I have used, Xsane always started to receive data as soon as the scanner starts exploring the document.

But in Kubuntu 18.04 Xsane waits to start receiving data until the scanner has finished exploring, which it makes much slower to scan several documents.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xsane 0.999-5ubuntu2
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: KDE
Date: Wed May 16 10:02:27 2018
ExecutablePath: /usr/bin/xsane
InstallationDate: Installed on 2018-05-07 (8 days ago)
InstallationMedia: Kubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
ProcEnviron:
 LANGUAGE=es
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=es_ES.UTF-8
 SHELL=/bin/bash
SourcePackage: xsane
UpgradeStatus: No upgrade log present (probably fresh install)