I Used this tool:
http://www.mympxplayer.org/rockchip-...7xx-df896.html
and i edit the BMP0.bin thing under the resources folder in the firmware partition. Images have to be 320*240 i think but i dont really remember. Its real easy to use. Also with the bug that yours has have you tried recalibrating it? One of mine has that same problem after being left alone for a while but recalibrating usually temporarily fixes that. Also there are a few firmwares here for the players that look like this. I uploaded two and there was another from tinydeal. maybe one of these can help. But also try asking the person you bought it from if they can supply you with a new firmware or player first. BE SURE TO MAKE BACKUPS OF YOUR ORIGINAL FIRMWARE FIRST.