Hi,

I'm experiencing an intermittent issue with the PDF reader.

Environment:
- Zotero 9.0.6 (ARM64)
- macOS 26.5.2 (stable release)
- No extensions installed

Behavior:
- PDFs that were working normally suddenly stop opening in the internal PDF reader.
- The files themselves are not corrupted.
- They open correctly in Preview/Finder.
- Annotations and indexing are still present.
- The problem affects existing linked PDF attachments.

A strange observation:
If I use "Add Attachment → Link to File..." and select the exact same PDF again, the newly created attachment opens correctly. Sometimes, after doing this, the original attachment also starts opening again. Later the problem may reappear.

Debug ID:
D1600651757

Relevant errors:

TypeError: can't access property "type", tab is undefined
chrome://zotero/content/tabs.js

TypeError: can't access dead object
chrome://zotero/content/xpcom/reader.js

There are also repeated occurrences of these errors throughout the debug log.

Please let me know if you need any additional information or a minimal reproduction.