Some of the “frame” values in the exported JSON are wrong.
I am using the macOS Steam build, v188.8.131.52.
Please find a ZIP containing the Aseprite doc, the exported files, and a screenshot of my export settings here.
If you search the JSON for “test-02 (aaa) 0.aseprite,” you’ll see that its frame values are 0, 0, 20, 21 – which are correct. However, the values for “(aaa) 1” are 0, 0, 256, 256 – which are incorrect. I’m not sure if it has to do with linked frames… However, a different layer – “(bbb)” – also uses linked frames and doesn’t appear to have this problem.