Steps to reproduce:

With a Handy Tech display attached and running:

1. Create a new message in Thunderbird and write some text.
2. Tab around the UI, out of and back into the main text area. Note that you may have to repeat this a few times.

Actual behavior:

After some tries, the Braille display stops working, I hear one or more error sounds emitted by NVDA, and even restarting the Braille display doesn't fix the problem. auto detection of Braille displays is broken until I restart NVDA.

Expected behavior:

Braille display continues working and doesn't suddenly fail.

NVDA logs, crash dumps and other attachments:

the following is logged in the NVDA log file:

LookupError: Object has no text descendants
ERROR - stderr (12:41:48.263) - hwIo.ioThread.IoThread (13352):
Exception in thread hwIo.ioThread.IoThread:
Traceback (most recent call last):
File "threading.pyc", line 926, in _bootstrap_inner
File "hwIo\ioThread.pyc", line 201, in run
OSError: exception: access violation reading 0x1BF30058
ERROR - core.CorePump.Notify (12:41:48.678) - MainThread (19800):
errors in this core pump cycle
Traceback (most recent call last):
File "core.pyc", line 750, in Notify
File "braille.pyc", line 2653, in pumpAll
File "braille.pyc", line 2414, in handlePendingCaretUpdate
File "braille.pyc", line 2423, in _doCursorMove
File "braille.pyc", line 2431, in scrollToCursorOrSelection
File "braille.pyc", line 1645, in scrollTo
File "braille.pyc", line 1686, in updateDisplay
File "braille.pyc", line 2273, in update
File "braille.pyc", line 2194, in _updateDisplay
File "C:\Users\marco\AppData\Roaming\nvda\addons\BrailleExtender\globalPlugins\brailleExtender\patches.py", line 563, in _displayWithCursor
self._writeCells(cells)
File "braille.pyc", line 2242, in _writeCells
File "braille.pyc", line 2247, in _writeCellsInBackground
File "hwIo\ioThread.pyc", line 121, in queueAsApc
File "hwIo\ioThread.pyc", line 77, in _getApc
RuntimeError: Thread is not running

System configuration

NVDA installed/portable/running from source:

Installed.

NVDA version:

version alpha-28166,e77bde9a

Windows version:

Windows 11 22H2 (10.0.22621) workstation AMD64

Name and version of other software in use when reproducing the issue:

Thunderbird beta 113.0B5. I've also seen this happen in Firefox Nightly on occasion, but the Thunderbird usecase is more reproducible.

Other information about your system:

Handy Tech ActiveBraille 2021.

Other questions

Does the issue still occur after restarting your computer?

Yes.

Have you tried any other versions of NVDA? If so, please report their behaviors.

No, as I didn't want to loose the speed improvements in the current alphas compared to 2023.1.

If NVDA add-ons are disabled, is your problem still occurring?

Yes.

Does the issue still occur after you run the COM Registration Fixing Tool in NVDA's tools menu?

Yes.

CC @jcsteh