The attachments' name did not match between the view window and the right panel.
I used the 'Rename file from parent metadata' by right click, I found that the name of the file has been changed as shown in the right panel, and the name is also changed after I check the local disk, but in the view window, the name did not change. The issue applies to both 'PDF' and 'snapshot' attachments. Please see the following figure:
https://s3.amazonaws.com/zotero.org/images/forums/u6195194/1dzl8ilf4deptult2ehn.png
https://s3.amazonaws.com/zotero.org/images/forums/u6195194/1dzl8ilf4deptult2ehn.png
https://s3.amazonaws.com/zotero.org/images/forums/u6195194/2sxb6mosz2oel8nyj79p.png
https://s3.amazonaws.com/zotero.org/images/forums/u6195194/fv5l0zd24k6is37m7gdq.png
You can manually set the title to whatever you want from the item pane, but Zotero 7 won't set the title to the filename.