Hello. This is not easily reproducible, but I will update the topic when I find a way.
When returning to Glyphs after switching to a different app, the filters/search function in the font view have no effect. The group of displayed glyphs doesn’t change, it stays on the old selection.
Re-opening the file works, but it doesn’t start working again on the other file I still have open. I need to re-open that one too.