Speedometer screen Problem with my Hyosung GD250R

Hello everyone. The screen of the bike started flashing on and off randomly. Then it stop working completely. However, later on the screen started not to turn off when I switch the engine off and drained the battery more than once. I have replaced the battery as I thought it might solve the problem but unfortunately it was not the issue here. Please help. I went to many mechanics around and they asked me to change the whole speedometer screen. But if it’s not functioning then why it drains the battery?.