PowerPoint 2021 crashes when saving .ppsm files containing ActiveX controls

Hello,

I believe I found a regression in recent Office 2021 builds.

PowerPoint crashes every time I try to save a macro-enabled presentation as PowerPoint Show (*.ppsm) if the presentation contains Microsoft Forms (ActiveX) controls, such as:

• TextBox
• ComboBox
• CheckBox
• etc.

Troubleshooting performed

Microsoft Support already assisted me through two remote sessions.

We tested:

• Office license validation
• Online Office Repair
• New Windows user account
• Registry checks
• Windows services

None of these resolved the issue.

Reproduction

1. Create a new PowerPoint presentation.
2. Insert an ActiveX TextBox or ComboBox from Developer → TextBox.
3. Choose Save As → PowerPoint Show (*.ppsm).

Result: PowerPoint crashes.

Tested Office versions

• Office 2602 (19725.20172) — Windows 11 21H2 — ✅ Works
• Office 2606 (20131.20154) — Windows 11 25H2 — ❌ Crash
• Office 2607 (20228.20110) — Windows 11 21H2 — ❌ Crash
• Office 2607 (20228.20110) — Windows 11 23H2 — ❌ Crash

I reproduced the issue on three different computers.

The last known working build is 2602 (19725.20172).

The first confirmed failing build is 2606 (20131.20154).

Saving as .pptm works correctly. Previously created .ppsm files also open and save correctly. Only creating or converting a presentation to .ppsm triggers the crash. If needed, I can also provide a minimal sample presentation that reproduces the issue.

Thank you!