cannot change default application to open XML files

[Tomislav]

.xml file -> right click -> Properties -> Open With -> Related Applications -> GVim -> "Set as default"

Expected behaviour: GVim shown as the "Default application" (instead of Firefox, as is currently the case)

Observed behaviour: Firefox remains the default application

The problem only seems to affect .xml files and is unrelated to GVim (if I select "Text editor" instead, Firefox still remains the default).

Workaround: open file from bash

Repeatability: 100%

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: nautilus 1:3.26.3-0ubuntu4
ProcVersionSignature: Ubuntu 5.3.0-51.44~18.04.2-generic 5.3.18
Uname: Linux 5.3.0-51-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.15
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Mon Jul 20 16:53:35 2020
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-xenial-amd64-20160624-2
GsettingsChanges:
 b'org.gnome.nautilus.preferences' b'default-folder-viewer' b"'list-view'"
 b'org.gnome.nautilus.window-state' b'sidebar-width' b'218'
 b'org.gnome.nautilus.window-state' b'geometry' b"'1189x576+66+93'"
 b'org.gnome.nautilus.icon-view' b'default-zoom-level' b"'larger'"
InstallationDate: Installed on 2018-05-10 (802 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: nautilus
UpgradeStatus: Upgraded to bionic on 2020-03-04 (138 days ago)
usr_lib_nautilus: