Can you give me some ideas for debugging these problems?

Can you give me some ideas for debugging these problems?

[Linux for blind general discussion]

Hello John,
I think I may know your problem. I have the same display,
and I was having usb problems. It almost drove me sane.
Finally I replaced the usb cable with a cheap cable from Walmart,
and that fixed it. Now I am thinking those cables
vispero supplies may be defective, but mine worked fine for a while.
try replacing that cable. Good luck.

Can you give me some ideas for debugging these problems?

[Linux for blind general discussion]

Helloo Everyone,

I will first describe the problems and then ask some questions. I don't claim to be a Linux expert. My ignorance will be evident to the real experts.

I have a Debian Buster system with 8 GB of memory. It is less than four years old. Recently I installed Gnome 3.3 with Orca. I use Braille only and no speech, 
since I am deaf-blind. The Braille display is a Focus 40 connected to a USB port. A technician from a local computer company installed TeamViewer so he could help 
with problems remotely, but he seems puzzled by the ones I am encountering.

When the system boots the desktop comes up on tty1 and ty2. It appears to be functiooning fairly well. TeamViewer is running and asking for a partner. I can run 
Firefox and surf the web. However, eventually the Braille display becomes unresponsive. It keeps showing the same thing, no matter what I do on the keyboard. 
Sighted companions tell me the screen is responding appropriately.

I can switch to other consoles using ctrl+Alt+Fn and run command-line programs. However, when I switch back to tty1 or tty2 the Braille display acts as if the 
USB port has been disabled. It appears to have been turned off. Switching to any other console produces the message "no irq handler for vector and BRLTTY5.6. 
After a while the console behaves normally for command-line use. The desktop seems to disappear completely. I can switch consoles with Alt+Fn. Except to tty1 and 
tty2, which hang up.

Questions:

1. How is the desktop started at boot time? What script or program starts it and how is it called?

2. The problem with the Braille display becoming unresponsive and continuing to show the same thing must be a problem with Orca. It apears to work properly for 
the most part, but I can't use help mode. I have asked about these problems on the Orca list, but they were no help.

3. The desktop runs functions from several libraries. Which of those might be crashing? How is it possible for something not running as root to produce an 
interrupt with no handler?

Thanks,
John

-- 
John J. Boyer
Email: john.boyer@abilitiessoft.org
website: http://www.abilitiessoft.org
Status: Company dissolved but website and email addresses  live.
Location: Madison, Wisconsin, USA
Mission: developing assistive technology software and providing STEM services 
        that are available at no cost