After the last two updates (3.5 3514 and 3513), I’ve noticed what seems to be a bug.
I usually have a document open containing several open tabs when I get a notice that there’s a new update. The document is still open as the update is downloaded. When I click the relaunch button, the document is automatically reopened as Glyphs starts up. But all the tabs that were open previously are gone. The workaround I discovered is to close the document and reopen it—all tabs are restored.