It could be a bug or incompatibility, but there are some other subtle problems in your project(s) that may be affecting you.
Incidentally, there is no such thing as a "static framework". A framework is a dynamic library packaged as a bundle. Perhaps you mean a private framework (a framework embedded in an app bundle, so not shared between apps, which is very common), or a static library (which is a collection of object files, a "library" in the Unix sense, not in the Apple sense).
— One possibility is that the deployment target got changed when you converted the framework project for Xcode 9. This might result in an incompatible build product.
— Another possibility is that your are not producing the framework using Archive (from the Product menu), but are trying to use the build product from a Build or Run operation. The difference is that Build might not build all of the CPU architectures that a finished (Archive'd) framework needs — the variant for "arm64" might actually be missing.