If a SINE sample is giving you problems and you are advised by OT Support to delete the library.json file (only if instructed) and reconfigure the collections.
a) Do the +Collections for all drives containing OT SINE libraries (or else some will be missing) and
b) In your Dorico project clear all the articulations for the patch that was giving you problems and reselect them. This should correct any problems it was causing but then you should immediately save the Dorico project. This is because, like Reaper, Dorico seems to remember the previous defective version of the articulations so you must clear them, reselect them, save, quit Dorico and reload the project.
Thanks to OT Support for helping me resolve the problem with BS Celli Longs and Shorts. Somehow either there was an error with the original BS download or the files concerned had become corrupted. The virtual keyboard was blank with no sound for some reason but the problem is now resolved.