The attempt to save the TiddlyWiki with CTRL+s triggered the usual file save dialogs.
The file on the disk after that had the expected time stamp.
In the browser UI the button "Save changes" still was shown in red, which looked suspecious.
When closing the browser tab with the TiddlyWiki a warning is displayed, that the contents was not saved. User closed it anyway.
Opening then the TiddlyWiki file resulted in messed layout and broken functionality (buttons, e.g Create a new tiddler non functional, selecting from Tools list without effect ...).
Practically the TiddlyWiki file is no longer usable.
Is there a way to add a trap for the browser shortcut CTRL+s ?