Here’s one discussion I found (I’m pretty sure there were others … you can try searching for “yall” or “lambda”:
tl;dr: library(yall) doesn’t know about other expansions, such as for dicts, so the generated code can be different than what you expect (and there are differences between lambdas in compiled code versus in interpreted code (inside a call/1)). So, it’s worth using listing/1 to see what term expansion did with your code.
This doesn’t account for the SEGV, of course – that shouldn’t happen under any circumstations.