Just a quick (dumb) question: is this 'tinning' silver? Or Green? In
other words, has the solder itself actually flaked off the trace (meaning
it never bonded in the first place) or has the 'paint' coating called the
solder mask, which is usually green, come off, revealing the trace beneath
it? This very common, and Ethan is right, it should be carefully re-tinned
to avoid long-term corrosion.
Cheers and Best of the Season
John