Do you get any output during the three seconds before the time slider stops? I guess you don't.
Interestingly the play/pause button still displays as pause, so the WiiM Home app recognises the Ultra as still playing (although there is no progress on the time slider).
The screenshot shows you using the Tidal integration into the wiiM Home app. I'm sure you are getting the same result with Spotify Connect and using the Tidal app and Tidal Connect instead?
If so and since the WiiM Home App is fully functional otherwise, this is probably the right time to file a ticket with WiiM.
Unplug the power for a minute or so, then reconnect. Let the Ultra boot up. Start playing any track from Tidal or Spotify and when the progress bar has stopped, tap the three dots in the lower right corner (More) and then Send us feedback. Not only can you describe the problem here but the device logs will be sent along, giving WiiM engineering something they can analyse.
You will receive an email when your feedback was received. Read this confirmation mail thoroughly and reply to it. This way you tell.WiiM support to contact you directly (and not just to develop and role out a fix).