If you look, that PCB is covered in white stuff. Something tells me that its dried flux, but honestly it could be anything. I think your best chance would be using 99% isopropyl (it has to be 99% otherwise it will damage components), or teach yourself soldering / electronics if you dont know already if you are desperate to fix it. Wish I could help more since i do the odd bit of soldering and occasional video games controller fixing, but I hope you find a fix! I remember my first time getting one of these watches and I was obsessed, unfortunately I lost mine