Save As filename empty after digital signature on macOS Tahoe 26.4.1

After updating to macOS Tahoe 26.4.1, the "Save As" dialog 
shows an empty filename field after applying a digital 
signature in Adobe Acrobat Pro.

Setup:
- Mac mini M4 (2024)
- macOS Tahoe 26.4.1
- Adobe Acrobat Pro 26.001.21529 (Universal, Apple Silicon)

Steps to reproduce:
1. Open any PDF
2. Apply digital signature
3. Save As dialog appears with EMPTY filename field
4. Cannot even paste text into the field

Same Acrobat version on MacBook Pro M2 with macOS 26.3.1 
works correctly - filename is auto-filled as expected.

Issue started immediately after macOS 26.4.1 update. 
Reinstalling Acrobat (including clean install via Creative 
Cloud) did not fix the problem.

Business impact: We sign 50+ PDFs daily. Manual filename 
entry is not workable.

Please prioritize a fix.