Etronix power pal charger problem
 

I bought a 4 channel power pal charger and all was working well until last night when 2 of the screens went blank
screen 2 and 4 do not show anything but yet the buttons still work as you can hear the beep when you press it

has anybody experienced this before?
can i fix it ?
Do i have to send it away?

It was a used purchase but was working fine for the last few months
Both other channels still charge and display fine

please help