I've been having issues with my rudder off and on since getting my boat six months ago.
As I've dissected the rudder system and the control lines in greater and greater detail, I've found that the knots used on the control lines are not appropriate and in general not safe for long term use.
The most widely used knot is the overhand knot http://en.wikipedia.org/wiki/Overhand_knot
. The key problem with the overhand knot is it's strength. It causes a 50% reduction in line strength due uneven wearing and stretching. Over time, this will increase until the line FAILS.
Much better would be the figure eight knot http://en.wikipedia.org/wiki/Figure-eight_knot_%28ropes%29
. It causes a 20% reduction in line strength.
The blood knot which is ideal for slippery line like spectra or monofilament line and causes a 20% reduction in line strength.
The bowline, double bowline, double fisherman's knot, carrick bend, sheetbend, and double sheetbend could also be considered.
I found that overhand knots were used in the running length of a line merely to shorten the line. This is something that a knot should NEVER be used for because it weakens the line. If it has to be done, at least use a knot appropriate for the use and that does the least damage.
I think that with all the sailing experience Hobie has they would know better.
I have ordered new spectra cord and will be replacing all of the existing rudder line. I think I will also install a turnbuckle in the system to tension the lines