Confirmed at this end as well, but I had commented enough. One reason why you couldn’t make/keep your shading domains.
For if you attempt to flip the normals etc after you have designated your shading domains, you will loose them, that’s why it is important to check/adjust your normals prior to designating any SD and/or mat’s. Why one should only designate SD/Mat’s after you have finished modelling, but prior to UV’ing.
Well, I’ve tried various ways to add tessellations to the shirt & on every attempt it crashes Hexagon. If you/or anybody else has similar problems then to be brutally honest, I think you should start again you will find you will create the mesh twice as quickly as this one. There is in my humble opinion something seriously wrong with this mesh and its not, too many poly’s.
EDIT: Doh!!!!! I’m a twit, I’m a prat, I’m a wrinkly idiot; you’ve collapsed the DG. I’m attempting to add tessellations to a smoothed mesh = wrong! One silly nearly 73 year old man will now shut up and slink away with tail between legs. I should be put down mutter, mutter, dribble. Perhaps I’ll pop my clogs before they come to take me away.
Seriously; make a new mesh.