Steps to reproduce:

1( Restart PC.
2( Restart NVDA.
3( Open attached Excel file.
Excel読み上げテスト_データマッピング.zip
4( Now BQ60 cell is focused.
5( Press left arrow key 9 times to move to BH60 cell. NVDA said "BH60".
7( Then, press left arrow key to navigate to left side cell.
8( Press left arrow key again.
9( Press left arrow key again.
10( Then, press right arrow key.

Actual behavior:

At step 7(, NVDA said "BH60".
At step 8(, NVDA said "BG60".
At step 9(, NVDA said "BF60".
At step 10(, NVDA said "AE60 through BE60".

Expected behavior:

At step 7(, NVDA should say "BG60".
At step 8(, NVDA should say "BF60".
At step 9(, NVDA should say "AE60 through BE60".
At step 10(, NVDA should say "BF60".

System configuration

NVDA installed/portable/running from source:

NVDA portable
Synthesizer: Windows OneCore Voices
Voice: Microsoft David

NVDA version:

NVDA 2020.4

Windows version:

Windows 10 version 1909 English

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

Microsoft® Excel® for Microsoft 365 MSO (16.0.13231.20620) 32-bit English

Other information about your system:

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.

Same issue happen with NVDA version 2020.1, 2020.2 and 2020.3 and does not happen with 2019.3 and earlier version.

If addons are disabled, is your problem still occuring?

No addons are installed.

Did you try to run the COM registry fixing tool in NVDA menu / tools?

No because it happen with NVDA fresh install.