Unforetunately your issues are exactly identical to mine that I experienced a year ago. I called Merlin at St. Charles and the do not make those cores anymore due to their faulty design. In order to replace it you must replace the entire unit to include the controls. The cost was in the upper $300.00 range and that did not include labor. I still haven't replced mine due to the cost.

1995 Honda Passport;
Some people wait a life time for their ship to sail in, while others simple grab the oars and begin paddling
Yours truely
http://www.zutah.com