&gt;to see if it's more prone to do that than the awk random number generator
I doubt there is any significant difference. Certainly not any that would matter for a project like this.

&gt;To be clear, you're not suggesting the pre/post increments work on busybox/ash correct - they don't appear to unless I'm doing it wrong:
I just threw up a Alpine container and at least there it works just fine. What command did you run that produced this error message?