Acrobat Pro 2026.002.21901 – Page thumbnail drag-and-drop failure linked to Protected Mode / HangFixGating ADC4552479

We have a reproducible page drag-and-drop issue in Acrobat Pro 64-bit 2026.002.21901 on Windows.

In Pages and Organize Pages, dragging page thumbnails to rearrange pages fails approximately 90% of the time. Acrobat briefly recognises the mouse-down/movement, but the drag immediately cancels. Other drag operations in Acrobat work normally.

We tested five similar laptops running the same Acrobat version. Two are affected and three work normally.

We have reproduced the following on both affected PCs:

Failing:
Protected Mode at startup = ON
HKCU\Software\Adobe\Adobe Acrobat\DC\HangFixGating\ADC4552479 = 1
→ page dragging mostly fails.

Working:
With Acrobat completely closed, change only ADC4552479 from DWORD 1 to 0, then launch Acrobat with Protected Mode still ON.
→ page dragging works reliably (20/20 attempts).

Acrobat automatically changes ADC4552479 back to 1 shortly after startup, before any PDF is opened, but dragging remains functional for that running Acrobat session. On the next Acrobat launch, when the value is already 1 at startup, the problem returns.

On a known-good PC, ADC4552479 is 0.

We have now also established that disabling “Enable Protected Mode at startup” completely eliminates the drag problem across subsequent Acrobat restarts, even though ADC4552479 remains 1.

Therefore, the issue appears to involve an interaction between Protected Mode and whatever internal Acrobat behaviour is controlled by HangFixGating\ADC4552479.

Standard troubleshooting has already been completed without resolving the issue, including Repair Installation, resetting Acrobat preferences/side panels, New vs Classic Acrobat, disabling Generative AI, multiple/new PDFs, external-monitor removal and display testing.

Protected Mode logs and registry exports from working/failing states are available.

Could this please be escalated to Acrobat Engineering? In particular, could Adobe identify what HangFixGating\ADC4552479 controls and advise whether there is a supported workaround that allows us to keep Protected Mode enabled?