You could try deleting the built-in folder (worked in my case).
From my experience. The settings are kept in the desktop.ist file, BUT, just deleting this file works once, but as soon as TC is closed the fault returns.
If you have never deleted the built-in folder before. Caution - this will reset TC to defaults. First. ensure you have your desktop workspace config saved if you have done any customisation from the TC defaults, and not previously saved it. Go to tools customise, options tab, note the tool icon sizes, under the save-in button type a name (I just use Andys), and click save-in. This will save any workspace you have altered, like any custom toolbars you have added. Close TC
Second. Navigate to the built-in folder, directions in this thread
. select the built in folder, and copy and paste it somewhere else, This is just in case this process doesn't work in your case, you can then put your existing built-in folder back again.
Third. Delete the built-in folder.
Fourth. Start up TC. This will automatically put a new built-in folder in place, Click new from scratch drawing, Go to tools customise, reset the icon size if necessary, load you workspace (select from dropdown list and click Load from), Set the Style and Theme to whatever you are used to, probably either Classic or Default, TC may reboot after altering. Close TC
Restart and see what happens.