Doesn’t matter where I try it, as soon as Cubase IC Pro is connected, my DAW has visual lags randomly, the audio playback/recording still works normally. Once in a while Cubase also crashes without Dump file. I tried to use Cubase IC Pro via App from the App store on an IPad, on a Samsung tablet via the browser using :45000 and directly on my DAW computer via localhost:45000 (so network connection cannot be the issue).
I think the problem is that Cubase GUI is also handling controllers. With the performance problems we have had in 10.5.0 the remote controllers using midi could see very sluggish remotes. It send to a some build-in device the that can not handle flow-control the impact will be that the gui stops. It usually considered bad design to have IO dependencies in a applications GUI thread.