On the OMPI users mailing list, Brian Larkins reported a segfault in btl-portals4 when running osu_latency.
The problem is a series of add_procs()/del_procs() calls that cause btl-portals4 to free top level Portals4 resources. Any additional add_procs() calls will trigger the segfault.
Brian reported this problem using v3.0.0, but it also exists on master and v3.1.x.