Why does my Ego 18" Chainsaw CS1800 chain bar keep loosening up?

I had this problem and discovered that the original Chain that came with the Ego 18" Chainsaw was stretched out.

First, I cleaned all the debris and crud out from the Tool-Free Tensioning System on the CS1800 chainsaw, to see if that was the problem, then gave the eccentric cam a shot of WD-40. Then I put the (old) original chain back up and tried tensioning things up. Felt exactly the same, and could barely get the chain to get tight around the chainbar.

So I decided to buy a new chain (in this case the Oregon S62 AdvanceCut Chainsaw Chain for 18-Inch Bar, 62 Drive Links). Once I got the new chain, I compared the old Ego chain that came with the chainsaw and the new Oregon S62 chain, and could tell that the old ego chain appeared to be about the same, but the Ego was a touch longer (essentially the Ego chain had stretched out). Once I put the new Oregon S62 chain on my Ego CS1800 chainsaw, I was instantly able to tension the chain easily. I did not have to crank down on the chain tensioner to get the chain tight, it simply took a few turns and the chain / chainbar was tight. This new chain solved the tensioner problem and the chain / chainbar loosening up and getting wobbly.