When I log in, I see every applet twice (clock, indicators, global menu). Attempting to remove one leads to both disappearing and I have to add them again manually. Logging back in takes me back to two of everything.
Running Ubuntu Mate 18.04 with the default theme.
Hi @lolwhites, I’ve been sitting on this for 4 months wondering why this board isn’t lit up with this issue. Except I’m unable to reliably reproduce it in a virtual machine. I have 2 native installs of 18.04 on a 2nd HD on this Dell XPS 8700 desktop that easily corrupts panels, mostly in this way.
So what do we have in common? Here’s some things I haven’t eliminated.
Dell XPS 8700 with nVidia Graphics.
Lots of memory, 24GB
Somewhat oddball 1920x1200 Acer monitor
The default theme is “Familiar” but I switch most between this and “Traditional”.
I do use compiz but it doesn’t seem related.
For awhile I was convinced it was the Weather Report applet at fault. But no more.
Saving/restoring panel layouts is the fastest way to corrupt panels.
dconf-editor clearly shows doubling of applets is usually two names like “window-list” and “windowlistapplet”. Or “clock” and “clockapplet”. Or “object-0” and “mateweatherapplet”.
To get back to stable, Open Mate-Tweak and under Panels select “Traditional” then back to “Familiar” (if one is loaded you cannot select it again but have to go somewhere else first). Does that straighten it out? If not, do it a few times until it survives a logout/login.
That is, I’ve found only loading a pre-set panel layout gets out of the corruption. Editing the panel seems to make it worse.
Anyone else?
Here's what I mean in dconf-editor.
This is plain old Traditional panel layout:
I saved this then restored it. Notice some duplicates now:
I saw the same issue after choosing the Mutiny layout in a clean installation.
Yes, I faced similar issue and the only way I was able to get back to normal was to load a pre-set panel.
@gabdub, @Apollonius Thanks much for your inputs. Is it rare or assured in your cases? For sure the best way for me to get this is to restore any saved panel layout on a native install (not a VM).
As far as I can remember, I set the Mutiny layout after installation, in a VM and on this PC, and in both cases the items were duplicated after rebooting. The only thing that solved the issue for me was to delete the duplicates manually using dconf-editor.
I can try to screw the VM at work and see if I can reproduce the sequence.
I prefer to leave this PC untouched 
I should have said I was using the Mutiny layout. The issue hasn’t reappeared since I posted it here, so not touching anything!
Since I come from a Windows background, I immediately switched to the “Redmond” layout after installing. Over time I happened to customize that panel and suddenly thought of saving it as own personalized layout.
Which I did. And I started experimenting again. Then when I switched to my customized panel layout, from the tweak, bam, everything doubled; even resetting panels or rebooting didn’t help except going back to a pre-set layout.
And this was on a native install, on my desktop which I’m using right now.
That’s it, I learned my lesson. I now have plank at the bottom and a topmost panel layout, which I is saved as a customized panel. If I were to do those things again, the “doubling up” will happen…
Sorry, Bill, missed your question about what we have in common. I think we have very little:
Intel NUC with native graphics
12GB RAM
Default theme
Using Marco
Thanks, @lolwhites. I know there’s a big difference here between a VM and native install which suggests something in the environment may be a factor. Yes, we are very different.
But it’s great to find others have seen this. And yes, I’ve had many inexplicable times when things do not do the same thing twice. This really makes it hard to reproduce.
After trying for almost an hour, I can’t reproduce the issue in my VM.
It looks like something save the items twice at some point after the installation.
It could be a problem with the installation program, I remember an attempt to choose the layout from the welcome screen that was removed because it didn’t work properly…
In did a clean install back in April when 18.04 first came out and the issue has only cropped up in the last couple of weeks.
@gabdub: Thanks much for giving it a try. It’s fleeting for you, too. Did you attempt saving then restoring a panel layout in Mate-Tweak? That’s the big cause for my 2 instances on this Dell desktop.
@lolwhites, any chance it started when modifying the panel already in place or restoring a panel layout in Mate-Tweak? Once stable, I’ve never seen a problem come up without changing something and it sometimes needs a restart to show up. In other words, a fresh boot corrupted always happens when I modified the panel in some way last session but it was fine when I shutdown.
Yes, several times and “sadly” works perfectly
I tried with and without rebooting between layout changes (from my custom Mutiny, Mutiny and Familiar).
Thanks again for the fantastic effort. I have some far out things to try like changing resolutions and comparing saved .layout and .panel files. I’ve been playing with this on and off for months.
This may be VERY significant. I took an 18.04 VM and set it to 1920x1200 like the problem native installs. Bingo! That VM is now very much like my problem installs.
When I load a previously saved custom layout the fun starts. First these two get out of sync:
org/mate/panel/general/object-id-list
org/mate/panel/objects
The first one is basically right but the second one has some items missing (which do not actually display) AND THOSE DUPLICATES like show-desktop and showdesktopapplet. No duplicates show at this time as they are not in that first list.
If I save this as a custom layout I assume it’ll be a corrupt one. The VM allowed me to see this first state but the native installs are well past this point.
Unfortunately, I won’t have much more time 'til the weekend. Anyone want to test a VM, set it to 1920x1200 and give it a try. I tolerated the resulting scroll bars but other modes may work, too.
I just reset the panel by switching to another layout and back to Mutiny. Customizations were lost, of course, but applets looked fine. When I logged out and back in, the applets appear twice, as does the wastebasket icon in the launcher. And the Mate menu has been replaced by the Caja launcher.
I’m not familiar with Mutiny but the trash applet is quite a common duplicate. I would guess switching again like that may straighten it out and it may depend on the temporary layout selected, too - it’s really been fickle like that for me.
I have a hypothesis the screen resolution is involved. My problem value is 1920x1200 so far. What is your screen resolution (it’s in “Displays”)?
My resolution is 1920x1080