I was wrong, my NPE is back. here is a repro: https://github.com/sritchie/programming-2022/pull/3 stacktrace is in the issue, but here is the top:

13 |          (sci/copy-ns demo.mathbox (sci/create-ns 'demo.mathbox))}
----------------^---------------------------------------------------------------
Encountered error when macroexpanding sci.core/copy-ns.
NullPointerException: Cannot invoke "clojure.lang.IFn.invoke(Object)" because the return value of "clojure.lang.Var.getRawRoot()" is null
	sci.core/copy-ns (core.cljc:376)

In case anyone's interested, here's a preview of my presentation about #nbb tonight (18:30 UTC) at London's Clojurians (online). https://www.dropbox.com/s/s6xa6530d16e4qy/nbb_lndc_2022.pdf?dl=0