I would venture to guess that in 99% of the cases, it's not multiple
routers showing up in a single hop but, rather multiple interfaces on
the same router showing up.
AFAIK, multiple routers showing up in a single-hop in traceroute response is
a sign of packet-by-packet load balancing, not flow based.
I could be wrong, though this was my past observation.
P.S.: What router-interacting applications are you using?