A little while ago I mixed up a 50ml batch of RWHY4. (A derivative of the recipe tc1 posted.) Poured it into a new 60ml bottle (that I just got today) and put it into the UC. After about the 4th cycle, for some reason, I decided to look at it. Well, apparently, I didn't have the cap on tight enough. Soup anyone?
On the plus side, I also successfully completed my first protank coil rebuild today. (Even if it does have one too many wraps.) Next time, next time. Got the second 50ml batch going now (smaller plastic bottles) and am checking the caps after EACH cycle. What, me paranoid? Nah, just overly cautious.