ISSUE:
On Boot or shutdown, sometimes after running different wares/apps/software/programs a error message is left on the screen with a mystery - what is it, why is it, how does one fix the unknown?
I do report them every time in hopes enough will raise the flag.
MY STUFF:
TIA
~i~
Crash files are stored and sometimes do not get cleared automatically when submitting the report.
“System program problem detected” Pop-up not going away
Delete files here: /var/crash
sudo rm /var/crash/*
You can look at /var/crash to see what has been creating your errors. Good luck Internaut.
Thanks @mdooley AND @franksmcb
the rest is comment based on personal observations and should NOT be taken out of context and used against me.
and sorry to seem dumb, but I cannot find a folder named " var" using "Files" or looking via "Terminal" so I searched it out and after learning how to find a log viewer, installed it and ran it, and I'm met with a long list of code from the "Important" tab on the left of the viewer.
Is there a quick trip to figure out what that -stuff- means?
This is getting to be way too much. Just to find the cause of the errors takes too many trips through too many sites (too many duplicating each others mistakes), and most don't come close thanks to 1984 serach engines.
Even to get a scroll bar width that isn't a hunt and click game trying to find it. Got that done, after a day of reading searching trying because most help assumes one knows what the helper is talking about.
I know everyone tries hard to assist, and maybe it's me, but I find it too time-consuming just looking for some thing like finding out what a errors is, and why and though easy for most everyone, "look at /var/...." results in my looking like a deer in the headlights or Homer Simpson's 'huh'" look 
I appreciate everyone's effort to assist. Just a hint though, some haven't learned the Ubuntu language yet, and for some, I wonder how many look at switching out Windoze, but run when they look through some support sites. It can be very frustrating, time consuming and hazardous if making a mistake. These irked ires gets blamed on Ubuntu.
Thanks again folks - when I have time, I'll tinker.
~i~
Only 36 shopping days left before Christmas - have a nice day 
Click on (expand) Computer, then File System and below file system, find the directory (folder) var. Click on var and find crash. Inside that directory you may see a bunch of files. These represent programs in your system that have crashed and produce the errors that you see.
Edit: Another way to get some sense out of what appears to be gobbledegook is to use the Mate Search Tool. As an example, I just opened it and entered ".crash" in the search field. Since I know where the search should lead, I did not bother to have the search carried out in my home folder (michael). Instead I searched on File System available in the drop down menu.
As with all the search results all over the 'net, a lot of what you say isn't there, but I figured out what you were seeing and guessed at what it might be on my version and found them THANKS!!
For others as new as I, I:
Clicked Files (there is no "Computer" on my desktop 'Mate')
In Files on left side, click "Other Locations".
There I found the "Computer" and clicked that and in that, found the VAR folder. In the VAR folder, as all have said, is the CRASH folder.
In the CRASH folder there are a few files.
I opened one with the generic text editor expecting to find a hint to the errors, but the files have so many lines of text, they take a long time buffering scrolling down and am met with:
SAMPLE copied:
Uname: Linux 5.0.0-36-generic x86_64
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
CoreDump: base64
H4sICAAAAAAC/0NvcmVEdW1wAA==
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
and so on. I think I'll copy & paste the whole thing into Google translator 
Off to figure out what they all mean... make that 6 espressos - got a date with a hot set of code.
Thanks folks - I'm learning; such as I learned patience, teeth grinding, hair pulling, new cuss words and that wine cures everything. Well, enough of it will at least for now.
~i~
This was a problem in 18.04 as well. It became so common for me I created a bookmark to "/var/crash" so I can easily delete these repeating messages.
Hello,
It might be a good idea, to remind those new to Linux, to read books on the Linux filesystem structure, before one dives into Linux. Here is a great start!
https://www.tutorialspoint.com/unix/unix-file-system.htm
Or you can add an alias to your ~/.bashrc file by adding this line:
alias ccl='cd /var/crash/ && sudo rm *.crash'
and reload the ~/.bashrc file with source ~/.bashrc in a terminal window and then you will be able to just type ccl to clear crash logs.
Unbelievable suggestion.
Important stuff is in BOLD.
Thank you @mdooley . Saved me hours pouring over novels looking for ways and means to understand why the error keeps popping up.
I gather then that the filename is the part-name of ailing culprit/s.
From .crash Properties I've pasted the filenames below:
Should I be researching even Google (same thing as search) for "nautilus-desktop.1000" and "shotwell" and scanning Disk2 for issues?
_usr_bin_nautilus-desktop.1000.crash
_usr_bin_shotwell.1000.crash
_usr_lib_udisks2_udisksd.0.crash ⟿ denies access to read, copy delete
Will copy out and delete other 2 with thanks also to @franksmcb.
~O~
p.s. Late responding - been busy recovering from a bad MoBo.
The name of the crash (nautilus-desktop, shotwell, udisks2) tells you what has crashed. You can keep notes if you like on stuff like this but what I do is delete these files IF they cause an error message. This kind of nagging stuff can get on your nerves.
I don't think searching will get you anywhere but you can try. Good luck.
The pop up message is Apport, Ubuntu's error reporting program. As @mdooley says, it's caught these applications (nautilus, shotwell, udisksd) from crashing. Sometimes it's a crash that happened in the background but auto-restarted.
They normally contain a "core dump" which is useful for a developer to know where in the code it crashed, so it's probably not worth your time researching unless you can easily reproduce the crash. If it's already reported using "Report problem..." then it should be on Launchpad ready for fixing in a future update.
Instead of clearing /var/crash/, it might be worth disabling Apport so it doesn't create crash files or show the error message:
The .crash file extension should be registered to Pluma by default, and Pluma should prompt for privilege escalation if you fail to choose "Edit as Administrator", like Mac & Windows do in similar contexts. This is not user-friendly and should not be that hard to fix.
We also need a more robust GUI for this scenario, similar to "WhoCrashed" for Windows, so the information is more accessible to the average user. This encourages learning and helps them to do their own research if they so desire.
However, it seems that you cannot create a shortcut to that folder on the desktop, as you would be able to do on Mac & Windows. It's all of the little nuisances like this which deviate from standard user interface conventions that tend to frustrate the refugees from commercial platforms.
