I get this error message when using the TreeShare for Ancestry window. I can reproduce it consistently on clicking the button "Options" and choosing "Clear everyone from changed list". (I did get the same error message doing a different function within TreeShare but don't remember exactly what it was. Most likely it was while syncing one individual.
I am using RootsMagic for Mac version 22.214.171.124 (25 Aug 2017). Because of this error I can't use TreeShare with the Mac version. (Tried same thing in Windows 10 with no issue.)
Has anyone encountered this and, if so, found a solution?