It's either a bum button board or the board the buttons are attached to. Many don't want to replace the 2 or so boards and live with remote only operation by unplugging the button board.
Hope this helps.
I have a Samsung LN32B360 that I have had since 2010 or so.
The last few months or so I have had it unplugged because it hasn't been working properly. It started with the TV randomly turning on and off when there was no input from the power button on the side and no batteries in the remote. After it did this for a while I left it unplugged for a few months.
I tried re-plugging it back in today and it is still doing similar things. The red light on the front would constantly flicker like there was some sort of input it was recognizing, but there was nothing being pressed anywhere. If I pressed the power button on the side of the TV, the TV would turn on and off, but it would also turn off when pressing the volume buttons. The menu of the TV would randomly open even if that button wasn't being pressed.
All of this is done by pressing buttons on the side of the TV, not the remote.
I took the back off the TV and reseated some of the connections. I set up my Chromecast and started streaming Netflix this afternoon. It would go from HDMI input to the regular coaxial/cable input every so often and I would have to change it back using the Smart Remote made by Peel on my Samsung Galaxy Note 4. It would stay on the HDMI input for 10-15 minutes then would automatically switch back to the coaxial/cable input.
Should I throw this thing away and get a new TV or what?