`CHANGE_TRACKING = AUTO` fails to populate full-text index
You said that the SQL Full-text Filter Daemon Launcher - FDHost is restarting. Do you have any error in the Event Viewer that would suggest it doesn't have the appropriate rights to run? 

You could check the account and password and check that the permissions are sufficient on the computer it runs.

You should check that the named pipes are enabled. 

For example, the documentation states that :


  If named pipes functionality has been disabled on the local computer, or if SQL Server has been configured to use a named pipe other than the default named pipe, the SQL Full-text Filter Daemon Launcher service might not start.


It also says that you can have problems if another instance of the same named pipe is already running.

If you can provide additional error logs, maybe we could help you futher.

I read a post here that says that this error got resolved once the SQL Service, Agent Service and Full Text Service all run on the same account. Maybe it's something worth trying.

You can try to query sys.dm_fts_fdhosts or another of the DMV views related to fulltext indexes. Maybe you can find additionnal information on what's going on there.