iPad app - Focus: many buttons' popup windows not sticking

Using Focus on the iPad app (Air 2), all right hand buttons (performers, composers, productions etc), nor the top bar Tag button, were not working on the first day I used the app. The popup windows would appear for a fraction of a second and pop away again, even if pressed repeatedly. The second day I used the app, they didn’t work first time pressed but they did work after a second press, and continued to work.

Not too worried as it seems to work now, but wanted to post this anyway, in case someone else has the same issue, or the issue returns. I’ll try again tonight and will add my findings to this post.