During my latest research I found a tiddyl file TiddlyFor-5.1.17.html.
Upgrading core by dropping the core js script onto the TiddlyFor-5.1.7 file to version 5.2.7 resulted into a RED marked error message:
Internal Javascript Error
Well, this embarrassing. It is recommended that you restart Tiddlywiki by refreshing your browser.
TypeError: self.addindexer is not a function.
close
Well, refreshing the browser results in showing the error message again and again.
Well how to resolve this problem ?