Hi Bob,
Sorry to hear what you're going through.
Revisional surgeries do tend to be more complicated and prior scarring can certainly be a problem. That said, endoscopic surgeries carry higher risk of nerve injury than open ones, by nature of the field being practically invisible. Choose a surgeon who has "many" of them if you go this route.
Have you seen a peripheral nerve surgeon or one who can do a "scratch collapse" test to verify the problem area? They don't always recommend surgery, sometimes other treatments are adequate. Scratch collapse testing will verify progress.
The other possibility is to see a Physical Medicine and Rehabilitation doctor who is certified in musculoskeletal sonography. These doctors can look at the nerve under ultrasound and potentially treat without surgery if scar tissue is tethering or compressing the nerve. Google "hydrodissection" for carpal tunnel in your city or state. There are not a lot of these specialists out there so you may have to hunt for one but they are well worth it.
I hope you find relief soon!