Roku TV is buffering and exiting apps

I bought a Roku 40" HD LED TV less than a month ago.  The model number is 40R3C5.  So far we have been using mostly the Spectrum app and HBOMAX app.  The TV is struggling with both of them.  Within the HBOMAX app it will stop abruptly while watching a show.  Sometimes it comes back after several seconds, sometimes it comes back with just sound and no picture, often times it will get us out of the app and we have to go back in.  While watching a recorded show via the Spectrum app the other night, it got choppy for awhile, then came back but automatically turned on closed caption.  It did that three times during a hour and a half show.  I've gotten messages to go to settings and check wi-fi connectivity.  Every time I do this the connection test runs fine.  We have a 400mbs internet package, so our speed and bandwidth is fine.  I have a TV in our basement with a Roku box attached to it.  All the apps work fine on the Roku box.

Please help.  What is wrong with my brand new smart TV?  This is very frustrating!

Regards, Mark