HELP! Konica Minolta C6000 Faded print in one side only

Good day everyone,
My name is Jay,
Please can someone help me with what to do to correct Faded printing problem on KM C6000
When I print CMYK Color in 12x18 the other side is faded like the YK is fade and CM is not.
When I try print it in KYMC the MC was faded and KY is not.
But when I tried it in short size paper it print solid color.
The Drums, Developer and Transfer belt unit is almost new.
Also tried to reverse the transfer belt but still na faded print is on same side.

Please help T_T