I have 3 PDFs that represent a text I want to import as a User Tool, so I tried them all to see which gave the best results. In so doing, I ran into a Dropbox sync problem again. I don't think I can give an exact sequence to reproduce it, because it also depends on when Accordance syncs with Dropbox.
So, I import PDF A, look at the resulting User Tool—let's call it "My Tool", and decide to try PDF B instead. So I delete "My Tool" and import PDF B, creating a new User Tool called "My Tool". It looks better. At this point, Accordance syncs with Dropbox and tells me it will have to reload my session. I push Continue and let it sync. "My Tool" disappears from my library, although the file is not deleted from the "disk" (SSD). So that's a bug. My guess is that if a user tool is created, deleted, and recreated in one sync cycle, Accordance is confused about whether it should be created or deleted.
But the confusion continues. I quit Accordance, find the User Tool in Accordance Files, and double-click it to add it to Accordance. The program starts, adds the tool, and then wants to sync with Dropbox again. When it does so, it has once again deleted "My Tool" from the library.
To get out of this, I quit Accordance, deleted the User Tool from Accordance Files, restarted Accordance, and pushed the toolbar button to sync with Dropbox before re-importing PDF B.