Importing grunge glyph from Illustrator

I created a grunge style of my latest typeface in AI, but I am having trouble importing it to Glyphs. I am using AI CC 2019. I copy and paste a glyph, say, A, from Glyphs into AI. I then apply a texture. However, when I attempt to export the grunge version Glyphs, it either freezes or the umbrella spins forever. Please advise.

I suspect a problem with subroutinization. Read this tutorial, please:
https://glyphsapp.com/tutorials/creating-fonts-with-complex-outlines