DLGLOBAL ERROR Trying to dispatch event 17 to non-existent FSM instance! (osmo_ss7_as.c:118)
Thanks for reporting this!
You write that your network is working as expected, and that you see this error only at startup: that means you don't need to worry about this error.
Nevertheless, it seems to be a newly introduced non-fatal bug, from this fairly recent patch: https://gerrit.osmocom.org/c/libosmo-sccp/+/35348
We should fix that: https://osmocom.org/issues/6356
So thanks again for reporting! ~N