DSON Importer does have a cache location. You can see where it is in the Poser menu: Scripts->DSON Support->Import Preferences... You could try emptying it's cache, but I don't know how it will effect your saved files.

Thanks for a second test & opinion - gives me a reason to struggle on. I did have the 'runtine' set wrong at first, as I assumed DSON meant where is the Poser runtime, not the DAZ G2F runtime - that caused LOTS of trouble.  While I tried to clean up any old work files, I did not do a big search & destroy.
I'm not worried about 'saved' files ... as they don't really work well. So I'd much rather delete ALL old work as well as the cache - if it make life go better going forward :)