What type of repair did they do? If it was a lateral suture, I have been told they almost always loosen up. I only do TPLO surgeries on my pups and foster pups and they have never failed. I have had countless knee repairs on pups over the years. TPLO and arthroscopy is more expensive but, in my opinion, well worth it. Those surgeries are also only done by board certified surgeons who have had specialized training in those procedures.
Here is a link that explains the different procedures for ligament repair:
https://www.topdoghealth.com/library...-cruciate-acl/
The problem with not repairing them is the dogs end up with severe arthritis. They can walk on them, but even if they don't show pain, they are in pain.
A couple of links that the surgeon I use wrote about LP and Torn Cruciate Ligaments:
Yorkie Haven Rescue - Patellar Luxation Info Yorkie Haven Rescue - Cranial Cruciate Ligament Tear Info
I am sorry you are going through this....very frustrating for you...and for the pup.