Naim app time display freezes

I’m using v5.11 of the Naim app on an iPad Mini (iOS 11.4), controlling an ND5XS, with MinimServer as my UPnP sever. For a while now, not just with the current version of the app, I’ve found the time display and progress bar at the bottom of the UPnP screen have a habit of freezing mid-track. I can coax them back into life by closing and reopening the app, but this rarely fixes the issue for more than a few seconds. Has anybody else experienced this issue and found a cure, please?