Bought a used PS Vita Slim only to find out the Left Analog stick would ghost down continuously. Tried compress air, to blowing air ,to switching the Analog sticks still to have a ghosting problem. I could not play any of my games via Touchscreen or buttons. After a thorough cleaning I found out that half of my PS Vita was water damaged on the left side causing the malfunction.
Repair was tricky due to the number of problems water damage can cause. My first theory after research was change the analog stick. Switched the left and right analog and still the same problem. Noticed the Button Board was very sticky and ordered a fresh new one. After new Button Board was installed still no improvement and analog is ghosting continuously.
For my Final attempt to repair PS Vita Slim I did a little more research from watching a video replacing the shell with a new shell due to Water damage. I saw the repairman take a Q-tip with 90% Alcohol, cleaned the main Ribbon Cable under the battery that connects to the Button Board and Power Button. What I found out was that my Ribbon cable,Left Analog stick, and Button Board were all water damaged causing the Analog to drift /ghost. Another thing to watch out for: Your Ribbon Cable maybe dirty, loose, or have a short in it. I turned on my PS Vita without the back Touchscreen and tapped the ribbon cable. The Cursor from the analog went Super Crazy going everywhere on the Vita. I tapped the on the Ribbon Cable again and the Cursor from the analog stopped that annoying drift/ghosting. I put my PS Vita Slim back together carefully turned it on and Bingo! Working good as new.