Why is NWM reviewing my claim when my condition hasn't changed? Is it strange that they requested an in-person review?

I have paid NWM disability premiums for over 24 years. April 2016 while at work I experienced a cardiac event requiring CPR, resulting in fractured ribs. Earlier I had been diagnosed with NASH developing into moderate to severe Cirrhosis with portal hypertension and severe esophageal varacies. It is thought at the time of my event I was severely anemic and had a coagulopathy due to platelet thrombocytopenia resulting in a variceal rupture, or a gastric ulcer bleed. I developed chronic fatigue, moderate to severe abdominal pain, diminished mentation and at times momory loss due to evevated ammonia in my blood causing hepatic encephalopathy. I also have had a worsening tremor that prevent me from venous access, especially on newborns and todlers as will as arterial and central line access. Also I cannot administer central and prepheral nerve blocks safely. I was granted full disability Benefits from NWM, Soscial Securty, As well as a statement of total, disability from Sunlife Ins.Coro. A second plan the hospital provided but could not receive benefits due to circumstanses as to the date the policy went into effect. So NWM has been sending monthly payments for over a year, however now they want to review my claim and have hired a Privare Investigator to conduct a Field Interview. What is this about my condition has nor changed perhaps worse. Is this a common practice with NWM? What are they trying to accompolish? All physian statements are filled out in a timley manner. Because of my failing Liver I cannot take tylenol or NSAI for pain so I have been prescribed a narcotic pain pill for everyday use. What is NWM agenda, why am I being harassed daily? Now sent a log in wich im required to report my daily activities every two hours… Highly stressful… any insight?