Today I tried to understand better the code.
I see that there are a lot of garbage collections:
in the code, in Thumbnail Updator it is used twice each time.
I think that should be avoided because it slows down the Application.
I tried to remove all and it seems to better responsive.
Also I noticed that there are several constructors like status = new string() ; that can be more efficiently replaced by the empty string constant directly statu = "";
I do not know if this is the right place where to discuss these things.