Pour more thin slabs and have the oven set a little warmer than normal for the first few days under vac 90-96 deg. After a few days turn the oven down to 88.8. Do your pour out with more solvent can help sometimes too.
When you do the initial muffin dont let it get to huge, lift it and drop it quickly.
Dehydrated concentrates are typically always shatter, make sure your material is frozen and butane bone dry. For super shatter you need to remove the terps so running thru a media (magsil, bentonite, activated alumina, etc.) helps. Lower oven temps and immediate purge helps keep nucleation down.
really terpy strains have a tendency to nucleate.some terps are hydrophilic which means they attract moister into them, which can promote nucleation as well .silica 60 can help sometimes with hydrophilic terps but is not a fix all and will lighten your color too.agitation will also cause nucleation .there is nothing wrong with nucleated shatter in fact most of the time it has more flavor.