Timing chains stretch over time /mileage. This is normal. Too much can be a problem and cause late valve timing etc.
A severe case will allow the chain to jump on the sprocket. My thinking is if you so much as set eyes on an exposed timing chain, go ahead and replace it.
"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut