Why can’t I edit the boundary of Chambers County Texas?

I have editted several U.S. county boundaries now without a problem. But I can't make any changes to the boundary for Chambers County TX. I can't drag the county lines and then they keep disappearing. I have to wonder if there is something different about this county in OSM. My end objective is to get trinity and galveston bays included into the county - like this map shows: https://ccrb1.maps.arcgis.com/apps/PublicInformation/index.html?appid=bf89436119254252b5d61c8f7c4aa56e