Just to confirm: I pulled the crystal repo, tag 1.13.2, and built from source. I used this to build our app, and no more segfault.
Then I reverted only this patch: Fix misaligned store in `Bool` to union upcasts by HertzDevil · Pull Request #14906 · crystal-lang/crystal · GitHub and recompiled crystal. Then I built our app, and the segfault came back.
So I’m confident that this fixes our issue. 
Both using LLVM: 18.1.8