I've had this 4' smart level for many years and its always worked fine, though it doesn't get used much. The other day I went to use it and discovered that the spirit levels (both of em) are no longer full of that nice green liquid, but have gone clear. It looks like all the green has collected at one end of each tube and hardened. They still work, but are significantly harder to see. Has anybody run into this and is there a fix?