Welcome to the forum, David.
I recommend checking your iPad’s App Store to ensure that you do not have any Dropbox updates to install.
Then, please turn off the Wi-Fi on your iPad temporarily. You can do this via your iPad’s Settings.app. Doing so will stop your iPad from trying to sync to Dropbox, which might be the cause of the crashes.
Then, please open your iPad’s Scrivener app and unlink its Dropbox connection. To do this, please go to Scrivener’s main projects screen and tap “Edit” on the upper edge of the screen. That should have Scrivener show a small gearbox icon on the lower edge of the Scrivener interface. Please tap that gearbox and then choose “Unlink DropBox” in the options.
Scrivener will ask you if you want to “Delete or keep files?” If you choose “Delete,” Scrivener will remove all of the projects currently saved to your iPad. They will resync later. If you choose “Keep," Scrivener will move any projects to the “On My iPad” section of the main projects screen.
If you’d like to be doubly secure, you could use one of the methods on this Knowledge Base article to manually back up your Scrivener projects, just to be safe.
Next please turn Wi-Fi on again via the Settings.app on your iPad. Then, please return to your Scrivener.app’s main projects screen. Please tap “Edit” again and then the gearbox icon. Now, you should see the option to “Link DropBox.” Please choose this option.
DropBox will launch and tell you that Scrivener wants access. Tap “Allow.” Choose your DropBox folder and you’re done. (If you chose “Delete” in that earlier step, then all your projects will resync.)
This should be a one-time process. To put that another way, if you go through this process and Scrivener continues to crash, then please consider opening a help ticket. If you need to open a help ticket, please share a link to this post so that the tech-support person who selects your ticket can see the steps you’ve already tried.