I usually test on "red" after noting that beta is broken (and before reporting a bug), but I've not had luck with any of my recent issues being already resolved there. With some help I found that:
A. The hard crash is a bug with string() not detecting a cyclic array reference under specific circumstances.
B. The contributing factor is this - despite there being no write accessors in use, a copy of array is made, causing all kinds of chaos. Doesn't reproduce on an empty project easily. Very cursed.