It looks like you might be using Castable V2. A few of our users have noticed that Castable V2 has a bit trickier a time sticking to the build platform than our other materials. We’re looking into the issue, and Katkramer had a good fix in this thread. If you could also reach out to support just to notify them of the issue so we can get a better understanding of it, that’s always a big help and they might be able to provide more advice.