I'm having this issue as well.
I'm in my tree twice, one entry doesn't have any people attached (which happens to be the main ID) and the other one is where all my people are. I tried changing the main record from living to deceased in Family Search and I receive "Save Failed - Unable to save conclusion due to a server error."
When I tried to sync a death event for the main person in RootsMagic to Family Search, I received this error:
Unable to create tf entity conclusion. person with death cannot be the user's treePersonId, personid=XXXX-XXX
Any suggestions on how I can get this linked correctly so that the main person in my tree contains all the other people that I have added?
UPDATE: Issue resolved. I had to link the relationships to my root person on Family Search and delete the duplicate record. All is well!