Is it possible to use the load balancing feature of the router for insuring a permanent internet connection, when one of the two used WANs is going offline?

In detail: 

I have a location where we have two internet-connections (two WANs).

One of the connection is sometimes going offline for unknown reasons.

When we stream video, we have problems because of this.

So I intend to use the TP Link TL-R480T+  to balance between the two connections. The idea is, in case that  WAN A is getting offline suddenly, the router should automatically switch to WAN 2, so the internal LAN keeps being connected to the internet, regardless of the offline moments of the WAN 1. (WAN 2 never has problems, but has a poorer speed, as it is LTE, WAN 1 is better, as it is a DSL connection, but has unexpected outages of a yet not understood nature).

My worry is the following: will the load balancing system allow the video streaming connections to stay alive, or will this switching between WAN A (gone offline) and WAN B disrupt the video streaming and stop everything? Would I have to reconnect manually in the video-streaming session, or would it work continuously, so that we don't "feel" that a switching from WAN A to WAN B just happened? 

As far as I know, the load balancer can switch between two WAN's (as this is the intended main purpose of it) but I did not test it in a situation when a WAN just goes offline (and not only has poorer connection than the other WAN).

Thanks in advance for your reply!