I’ll put up a disclaimer and state that I have not particular insight into your issues, but some things do come to mind.
In a lot of ways the virus has screwed up a lot of things. Even though it has been a year, there are still a lot of unknowns in how appointment methodologies have changed. Some adopted new methods a while ago, but others more recently. Medical office staff may be short-handed and some may be working out of position. For places that don’t have large waiting rooms, I think the scheduling has changed in order to avoid crowds. My guess is that you are experiencing an intersection of all of these.
From personal experience, I have a bit of a parallel. 12 years ago when my wife was spending a winter with me in Taiwan, she had a bad bicycle accident that resulted in a spinal cord injury. It has been necessary for her to use a wheelchair for mobility ever since. Air travel with a wheelchair should be relatively straightforward, but it isn’t. What experienced people told us was that after you inform them of your needs, you need to check with them periodically to make sure that everything is in place. THEY WERE SO RIGHT!! We have flown 7 or 8 times since then and half the time when we checked, the airlines either got the details wrong or did not have the information at all. When you said that you called multiple times, that is exactly what you have to do. I don’t believe that people set out to do a bad job, but they can get compromised by circumstances and their surroundings…
I believe your reasoning is spot on. I’m tediously resolving a number of communication gaps between the providers. Im getting closer….