no vf export from glyphs 4

Hi, I can’t export variable fonts from a well tested family. When trying to export .otf Glyphs 4 crashes, showing a large log file which could be sent to Apple. When trying to export .ttf, Glyphs 4 tells me that a and its components are not compatible.

VF export from the same file works fine in Glyphs 3.

What version of Glyphs 4 is this? And what are you exporting exactly?
Can you send me that .glyphs file for testing?