Gedit deletes file on samba shares when using a plugin which uses WebKit2

What doesn't work

I use gedit to open an existing text file, modify it and want to save it. It fails with the error:

You do not have the permissions necessary to save the file. Please check that you typed the location correctly and try again.

When I check (ls or refresh in nautilus), the file is still there.

But there is an inconsistent state

• Server file system: ls lists the file and cat file shows the contents.
• Samba mount: ls lists the file but cat file outputs cat: file: No such file or directory.

When I then close gedit without saving changes, the file is removed from directory listing and from the server as well!

What works

• Opening and saving a new (nonexistent) text file on that share
  • Without closing gedit, saving it again
• Using another editor like Vim or Atom to edit an existing text file

System

Gedit 3.36.2 on Ubuntu 20.04

Samba implementation: dperson/samba (samba-4.11.8-r0 on Alpine 3.11.6).

Output of mount (capital strings replaced):

/etc/auto.SERVER on /shares/SERVER type autofs (rw,relatime,fd=6,pgrp=2085,timeout=300,minproto=5,maxproto=5,indirect,pipe_ino=45304)
//IP/home on /shares/SERVER/home type cifs (rw,relatime,vers=3.1.1,cache=none,username=USER,uid=1000,forceuid,gid=1000,forcegid,addr=IP,file_mode=0755,dir_mode=0755,soft,nounix,serverino,mapposix,rsize=4194304,wsize=4194304,bsize=1048576,echo_interval=60,actimeo=1)

Samba implementation: dperson/samba (samba-4.11.8-r0 on Alpine 3.11.6).

Plugin code

File ~/.local/share/gedit/plugins/test.plugin:

[Plugin]
Loader=python3
Module=test
Name=Test
Description=Test

File ~/.local/share/gedit/plugins/test/__init__.py:

import gi
gi.require_version('WebKit2', '4.0')
from gi.repository import Gtk, Gedit, GObject, WebKit2

class MyPreviewPlugin(GObject.Object, Gedit.WindowActivatable):
	__gtype_name__ = "MyPreview"
	window = GObject.property(type=Gedit.Window)

	def __init__(self):
		GObject.Object.__init__(self)

	def do_activate(self):
		self.htmlView = WebKit2.WebView()
		self.scrolledWindow = Gtk.ScrolledWindow()
		self.scrolledWindow.add(self.htmlView)
		self.scrolledWindow.show_all()

		panel = self.window.get_side_panel()
		panel.add_titled(self.scrolledWindow, "MyPreview", "My Preview")
		panel.show()
		panel.set_visible_child(self.scrolledWindow)

		self.handleTabChanged = self.window.connect("active-tab-changed", self.onTabChangedCb)

	def onTabChangedCb(self, *args):
		# NOTE the following line causes the error.
		# replacing it with `pass` removes the error
		self.htmlView.load_html("", "file:///")

Why is active-tab-changed callback called when saving a file?

Why is it possible that some side panel element can cause the saving process to fail?

Steps to reproduce

Create and active the gedit plugin described above. Close gedit.

container=$(sudo docker run -d --rm dperson/samba -p -r -s "share;/share;yes;no;yes")
ip=$(sudo docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $container)
sleep 1
sudo mount -t cifs -o guest,uid=$(id -u) //$ip/share /mnt
echo "blablub" > /mnt/file
ls -l /mnt

There should be a file file with write permissions.

gedit /mnt/file

Edit the file and try to save it. The error should be displayed. When you close gedit now, the file /mnt/file disappeared.

ls -l /mnt

When you are finished

sudo umount /mnt
sudo docker stop $container