Restart in Troubleshooting Mode (Help → "Restart in Troubleshooting Mode…”), which temporarily disables all plugins. If that fixes it, you'll need to identify the plugin that's causing it and then report the problem to the plugin's developer (and also let us know what it was).
Following these steps it worked and I see that the add-on that generates the problem is ZoteroPreview. I hope you can fix it because it is a good add-on.
https://forums.zotero.org/discussion/124123/right-click-bug-on-items-only-zoteropreview-plugin#latest