Hi James, I happy to hear you at least made some progress. There is no
obvious reason (that I can think of) why is should not work for you as
you originally specified your setup, therefore I suspect a configuration
error, rather than a bug.
If you need further help with with your setup running on more than one
box, please take a quick look at
https://osmocom.org/projects/cellular-infrastructure/wiki/ReportingBugs
I don't think in this case it's necessary to supply absolutely
everything listed there, but at least config files, and some traffic
capture. otherwise you leave others guessing too much and it's hard
(impossible) to help.