I think you have to accept it is defect. Go to a Sony certified repair shop, or when the costs for a repair are to high, but a new one. Sorry, but there is no such thing as a magic spell to cure your camera over the net.
Thank you. If this device will accept a memory stick, then the make is immaterial. As for overwriting files, this will only happen if the files have the same name as the ones already on the device. To be sure, rename the ones you wish to copy across before you do so - a simple alpha-numeric character at the end of each file name will do the trick. HTH
Remove the batteries, clean all the connection tabs and battery terminals-tips etc with a simple pencil eraser. Poor connections cause this symptom. There's a layer of corrosion that's not even visable that is common on these.