Dolphin bookmarks from USB hard drive don't work after restarting

And then don't work anymore.

This happens all the times.

If I remember well, it didn't happen with previous versions of Kubuntu (nor other Linux distros for the case).

Screenshot attached.

Operating system: kubuntu 20.04 LTS, 64 bits, Spanish language.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: dolphin 4:19.12.3-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Tue Jul 28 13:38:49 2020
ExecutablePath: /usr/bin/dolphin
InstallationDate: Installed on 2020-04-25 (94 days ago)
InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=es_ES.UTF-8
 SHELL=/bin/bash
 LANGUAGE=es
SourcePackage: dolphin
UpgradeStatus: No upgrade log present (probably fresh install)