mini box

My mini boxes are junk.   I have called so many times regarding issues and they are never corrected.  Everyone resets the boxes and then tell me they don't know what is going on.  One box simply no longer will receive a signal.   It is not the wiring because the TV on the wall in the room behind it works fine.  Another box will not show certain channel like 13.  The channel is scrambled.  All other channels work.   I called they reset the box and nothing.   No one can tell me what the message M.3.1.4 means.   They just want to sell me the in home maintenance plan so they can change the wiring.  I am a loyal customer for over 20 years and the fact you want to up my bill even more to sell me a maintenance plan before you fix the problem is a joke.   I feel like if I purchase the plan Cox will replace wires that were fine and claim that was the problem.   I am so frustrated and ready to cancel all service with Cox.    No one is helpful or honest.