excessive tension on rudder blade controls

I'm a New sailor having a blast with my Tandem Island.

The rudder steering and up/down controls all seem to be getting impossibly hard to operate. I feel like I'm going to rip something apart trying to get the rudder down. Any tips?

Tore into it a little today and found that the string that works the pulley system to operate the rudder (tandem up and down levers) are spinning the pulley and twisting around each other. I untied the knots, removed the twist, and all worked well. Now, I am noticing after just a few uses, the strings are twisting up again. What's up with this?

This is a used boat, and I replaced several of the worn strings, so it's possible I've strung something incorrectly.
Is there a special technique or knot that is used that prevents the strings from "spinning"?
Is there a drawing somewhere of how the strings should be routed?
I assume the pulleys have to hang and move freely (and can't be fixed) as movement is required to pull the rudder controller strings.

Your rudder lines might be twisted. Look through rear hatch, use phone or camera. If lines are twisted use search tool to find ways to fix line twist. Good luck.