Hi
I can gaurantee that the people who repaired your garage door did not know what they were doing (unless you are not lifting the door correctly)
When you change cables you ALWAYS replace both sides, & also add more tension too the main spring!!
Please look at www.garagedoor-spares.com we have full colour fitting instructions on the site on our to change cable & add more tension..
I hope this helps
richard
richard@garagedoor-repairs.co.uk
November 2008