Upnp Dropout

My Raspberry -PI , running Upnp on Volumio has far fewer Dropouts than my Rotel Rt12 Digital system.!
The Raspberry -Pi is , however, still prone to Upnp dropouts.
I have replaced my Router, upgraded my Ethernet wiring, all to no effect. In Fact , my typing at this keyboard, is causing the Upnp system to drop out!

My Raspberry-Pi , fitted with a HiFiBerry TOS , Digital Optical Audio Output , produces a sound indistinguishable from the Rotel Rt12, that is, when it is working! The Optical output has absolutely No Earth loop interference, when feeding my Asus “One” DAC. The Rotel is however , superior when used as an online/DAB/FM Source, with almost No Dropouts when listening to the Very High Quality BBC Radio 3 online!

The Raspberry-pi, running Volumio is absolutely perfect when running from a 128 Gb USB Stick, Every thing is played perfectly at every sampling frequency , with absolutely no dropouts! My Volumio, controlled by a Tesco Hudl Tablet, is , however, very difficult to use! In trying to select a piece of music I often , mis-finger, selecting the wrong piece, or I am sent back to the Volumio front screen, sullenly forced through all the selections again!

How to limit these Dropouts, and allow me to rationalize my system, and save my sanity?