I can indeed open multiple context menus in other places. But I cannot reproduce the bug mentioned in that post with normal right clicks. To reproduce, it must be very fast right-clicks.

For example, I can get the screenshot below by fast double-clicks on a single item in the Items Tree:

https://s3.amazonaws.com/zotero.org/images/forums/u265723/f1d1vyrcjm2v5im7yst1.png

Steps to reproduce:
1) Open multiple PDF Reader tabs so that Zotero is busy
2) Go back to the My Library tab
3) Fast right-clicks on a parent item with a PDF files attachment

This is in Troubleshooting mode:
Debug ID: D1183111434

[JavaScript Error: "Error: An error was thrown inside one of your components, but React doesn't know what it was. This is likely due to browser flakiness. React does its best to preserve the "Pause on exceptions" behavior of the DevTools, which requires some DEV-mode only tricks. It's possible that these don't work in your browser. Try triggering the error in production mode, or switching to a modern browser. If you suspect that this is actually an issue with React, please file an issue." {file: "resource://zotero/react-dom.js" line: 4000}]

[JavaScript Error: "Error: Waiting for reader failed" {file: "chrome://zotero/content/xpcom/reader.js" line: 977}]

Note that I can see something similar in Zotero 6, so it is probably not a new bug in Zotero 7 Beta:

https://s3.amazonaws.com/zotero.org/images/forums/u265723/x5uryq763a0o9xmfj5oo.png

https://s3.amazonaws.com/zotero.org/images/forums/u265723/v9q3g7wr8s35umcrjvtj.png

https://s3.amazonaws.com/zotero.org/images/forums/u265723/m51337z6jxv6t5ps2iha.png

Zotero 6.0.36
Windows 10