Dash help please

I didn't trust the factory gauge either so installed an aftermarket temp gauge. The temp pegs independently from the gas gauge so I'll look at the original sending unit and wiring.
Very confused. When you asked your original question were you saying the STOCK temp gauge pegs and the STOCK fuel gauge also sometimes does the same thing? later you say you have an aftermarket temp gauge and it independently pegs from the fuel gauge.

Maybe I'm missing something here which gauges are your issues with?