Steps to reproduce:

1. Install SAPI4 along with a synthesizer. The SAPI4 runtimes can be found at http://web.archive.org/web/20150910165037/http://activex.microsoft.com/activex/controls/sapi/spchapi.exe, and a free and legal synthesizer can be found at http://web.archive.org/web/20150910005021if_/http://activex.microsoft.com/activex/controls/agent2/tv_enua.exe.
2. Load sapi4.

Actual behavior:

The synthesizer loads, but NVDA crashes soon after.

Expected behavior:

No Crash.

System configuration

NVDA installed/portable/running from source:

Installed.

NVDA version:

alpha-21882,528d5708

Windows version:

Windows 10, Build 21327.

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

N/A.

Other information about your system:

N/A

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.

Yes, alpha-21877,8e4b189b works normally.

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

Yes

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

Yes.