Looks like the tv is damaged physically.

Does it do this on all inputs?

maybe you screw too much

I think the technical term for this is "fux0red"

💀 R.I.P. 💀

take it back

Yeah you definitely touched or shook something while mounting it. It's probably just the ribbon cables inside that got shaken ,if you're comfortable to open the tv, do so and clean it up and the ribbon cables pins gently from the inside.

I know exactly what happened there. Okay I have had this happen to me two different times. They were both old and with Samsung TVs. Short answer is get a new TV. Longer answers is someone else mentioned it in the comments about the ribbon on the inside of the tv is dislodged or has a lot of dust that has gotten into the tv. I’m a DIY tech head and in my opinion it’s not worth all the work of taking it apart and troubleshooting what the problem actually is then trying to find that part. I was able to fix one of the sets. The same tv three months later popped a capacitor on the power module board. I was done. New TV up! Yeah take it from me. I have spent hours troubleshooting and finding what the problem is just for something else to break a little later down the road. I hope this helps. Good luck.