What you seem to be experiencing is an issue with dropouts on your network. UC Surface will have a buffer "wait time" for a response from a router. It would almost be reproducible by say going within 10 feet (line of sight) of your router and everything works, but slowly but surely walk away from your router. You might see a decrease in response time between the mixer and UC Surface at a given point.
The best way to approach this is to make sure you are using a quality router, it could be one of the routers we support while steering away from the routers we do not, and making sure that the wireless channel is free of interference in the area you are in. Most times this is changing the channel on your router internally until proper connection at great distances can be achieved.
Below is a link to the network setup and troubleshooting area of our Knowledge Base for RM mixers. You can take a look at this area for other suggestions of better connectivity for your router.
StudioLive RM Mixer - Wired and Wireless Network Setup and Troubleshooting