Steps to reproduce:

Using NVDA 2021.3 Beta 1 (also 2021.2):

1. Set NVDA to use UI Automation to access Microsoft Word controls (in advanced settings)
2. Create a blank document in Word
3. insert a table (ALT+N, T, then 2x2 or greater)
4. Try to set column or row headers (NVDA+shift+c or NVDA+shift+r)

Actual behavior:

NVDA reports "C" (and a "C" is typed into the current cell in the table).
Log fragment:

IO - inputCore.InputManager.executeGesture (12:34:31.394) - winInputHook (29728):
Input: kb(desktop):shift+NVDA+c
IO - speech.speech.speak (12:34:31.407) - MainThread (27980):
Speaking [PitchCommand(offset=30), CharacterModeCommand(True), LangChangeCommand ('en_US'), 'C', PitchCommand(), EndUtteranceCommand()]

(No error generated)

Expected behavior:

NVDA should set the current cell as the start of column (or row) headers.

System configuration

NVDA installed/portable/running from source:

NVDA version:

NVDA 2021.3 beta 1 installed

Windows version:

Windows 10 (64-bit) Version: 2009, Build: 19043

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

Office 365 (64-bit) Version: 16.0.14430.20304

Other information about your system:

NVDA is set to use UI Automation in Word. With this setting disabled, setting column and row headers works as expected. Also if column and row headers have previously been set in a table, and NVDA is set to use UIA, NVDA does read the headings while navigating around the table.

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.

NVDA 2021.2 using UIA, won't set headers or read existing headers.

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