I'm using Unity 2019.2.3 iOS with Wikitude 8.7
Is it possible that the images that disappear look very similar to other images from the 12 that were included? If so, the algorithm might not be able to detect enough differences and merge them with some of the existing targets. Can you please try to add some distinctive markings on the banners that don't work, just to see if this is the issue?
Also, have you tried the same banners in our online Target Manager? Did you encounter the same issues there?
I'm trying to make an Image Target Library with the Unity WTC Editor consisting of 15 banners.
For some reason 3 of them vanish once I hit Refresh, the other 12 work and detect in the app, but I can't get these 3 to stay in the library.