From time to time the Insync folder is loosing its special folder symbol and it looks like a normal folder. This happens by a reset of the write protection flag of the folder.
It took a very long time to find out who resets this flag of the folder. Now I found out that it is the Insync app and the problem is easily reproducible. At least unter Windows 10.
On the Google Drive website you just have to move a file to the root of the drive. As soon as the Insync app synchronizes the changes the write protection flag of the base folder gets reset and it looks like a normal folder.
And before someone asks for log files: The support already has my log files from this (still open) problem: