QTC crashes with clang backend/sqlite errors

I have a git project where I made a series of commits, at some point when QTC scan the project on open it started crashing with :

~/qtcreator-4.10.0/bin/qtcreator
Warning: No kit '{18eb939b-89fd-41dc-a5a5-86abc87d44ea}' found. Continuing.
terminate called after throwing an instance of 'Sqlite::UnknowError'
ConnectionServer error: "QLocalSocket: Remote closed" "/tmp/QtCreator-tGgebE/ClangBackEnd-29704"
ConnectionServer error: "QLocalSocket: Remote closed" "/tmp/QtCreator-tGgebE/ClangRefactoringBackEnd-29704"
ConnectionServer error: "QLocalSocket: Remote closed" "/tmp/QtCreator-tGgebE/ClangPchManagerBackEnd-29704"
Aborted (core dumped)

I have another clone of the same tree that did not show this problem, I applied the commits one by one to see if I could identify a breaking commit - there is not one - it all works fine for the other clone.

Annoyingly even after deleting the project files etc and re-opeing the project the crash persists.

Is there a config file/db hidden somewhere that I can delete to get the project forgotten so that I can reconfigure?