Wow, what a splendid debugging! I hope you enjoyed it. It seems that these [1] [2] bugs are all having the same root cause then. Or maybe [1] is different, it would be needed to debug that similarly to ensure that if libz3-4 is related or not. But probably it is.
[1]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1016658 [2]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1020802
