There's no 'obvious error' reported back to the project.
In cases like that there is no log file from the scientific app sent back to the project.
Hence, there is nothing to analyse and the task is either marked as 'failed' or 'lost' after the due date.

Even the log snippets you posted do not clearly explain if/why the tasks got stuck.

So, how should the project decide what caused the failure.
It could be either (may be incomplete):
- hardware
- the OS
- VirtualBox
- BOINC
- vboxwrapper
- data from CVMFS
- scientific app

From the project's perspective there's only the overall task failure rate for the computer itself.
As already mentioned for this computer it is less than 1 % covering all possible reasons.

However, for Theory tasks, you can click on the "Graphics" button in the left hand part of the BOINC Manager, then a Browser window opens, there you click on "logs", and then on "running log" - this shows the progress of the task
This tip has been very useful for me.
Previously, I blindly aborted Theory tasks when lasting more than 5-6 days.
Then I read your comment (thank you very much) and explored "Show graphics" command and beyond at BOINC Manager.Congratulations for returning this overdue valid task and many thanks for your extended comments and images!

It was also the longest task reported on November 7th: 344.21 hours
That is: 14 days, 8 hours, 12 minutes, 33 secondsUnfortunately someone broke your record during the last 100 tasks:

Theory Simulation 4930 6784 3.52 (0.03 - 489.41)
20 days - 9 hours - 25 minutes

This is a bug in VirtualBox 7.2.4.

On a computer with AMD CPU there's no known workaround so far.
...
After more testing...
Looks like the downgrade left the 7.2.4 kernel module on the system.
It now works after a cleanup and a fresh 7.2.2 installation (package from VirtualBox).

The kvm_amd module must remain blacklisted.

Hello,

I downloaded the script theory-vbox.sh from link https://github.com/seanr22a/LHC-Theory/blob/main/theory-vbox.sh
Then I tried to run it with the following Terminal command:

sh theory-vbox.sh
And I got the following result:

-e

--- LHC Theory - USER ---- 2025-09-24 16:27:48 ------------------------------------------------------

| Events |
Slot Job id Total Processed Remaining Elapsed time Completed % Err
------------------------------------------------------------------------------------------------------
theory-vbox.sh: 101: Syntax error: word unexpected (expecting ")")
Some kind advice would be very appreciated

... What is it about this project's crunching that produces such wildly varying runtimes?...
It's a result of the scientific input which you get (by random) from the backend queues.
More details can be found here:
http://mcplots-dev.cern.ch/
currently in progress:
http://mcplots-dev.cern.ch/production.php?view=revision&rev=2922

Crystal Pellet, many thanks for the valuable information :-)

The issue resolved itself with new tasks.

So the issue must have been bad tasks.Your issue and of other volunteers is solved by implementing Theory v301.00 application.

This version fixes the upload issue.

Is this being addressed?
Yes, but not yet solved.