LG smart TV, Streaming app worked well not sketchy picture on PBS but fine on Fox 12

My BETA streaming used to work OK, not nearly as well as the cable TV, but just OK (slow in initialization and limited feature compared to cable ease of use).  The BETA stream works on Fox and other channels but PBS, channel 710, comes in with block noise picture where other channels come in clear.  I have reset both modem and TV, same results.