I have already done that, so that doesn't appear to be the problem. I see exactly the same problem even when I'm only starting up a single instance. Tor binds everything to the correct ip:port, but the reachability test always tries to connect to the .102 ip address.
Is it possibly something to do with the way that my network interfaces are configured? FWIW I haven't actually touched anything there, it's still exactly how it was originally provided to me by the host:
# cat /etc/network/interfaces
# Automatically generated by OnApp (2.3.3)
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address 50.7.178.98
netmask 255.255.255.248
broadcast 50.7.178.103
network 50.7.178.96
gateway 50.7.178.97
auto eth0:1
iface eth0:1 inet static
address 50.7.178.99
netmask 255.255.255.248
broadcast 50.7.178.103
network 50.7.178.96
post-up ip route add
50.7.178.96/29 dev eth0:1 src 50.7.178.99 table eth0:1_if
post-up ip route add default via 50.7.178.97 table eth0:1_if
post-up ip rule add from 50.7.178.99 table eth0:1_if
post-down ip rule del from 50.7.178.99 table eth0:1_if
auto eth0:2
iface eth0:2 inet static
address 50.7.178.100
netmask 255.255.255.248
broadcast 50.7.178.103
network 50.7.178.96
post-up ip route add
50.7.178.96/29 dev eth0:2 src 50.7.178.100 table eth0:2_if
post-up ip route add default via 50.7.178.97 table eth0:2_if
post-up ip rule add from 50.7.178.100 table eth0:2_if
post-down ip rule del from 50.7.178.100 table eth0:2_if
auto eth0:3
iface eth0:3 inet static
address 50.7.178.101
netmask 255.255.255.248
broadcast 50.7.178.103
network 50.7.178.96
post-up ip route add
50.7.178.96/29 dev eth0:3 src 50.7.178.101 table eth0:3_if
post-up ip route add default via 50.7.178.97 table eth0:3_if
post-up ip rule add from 50.7.178.101 table eth0:3_if
post-down ip rule del from 50.7.178.101 table eth0:3_if
auto eth0:4
iface eth0:4 inet static
address 50.7.178.102
netmask 255.255.255.248
broadcast 50.7.178.103
network 50.7.178.96
post-up ip route add
50.7.178.96/29 dev eth0:4 src 50.7.178.102 table eth0:4_if
post-up ip route add default via 50.7.178.97 table eth0:4_if
post-up ip rule add from 50.7.178.102 table eth0:4_if
post-down ip rule del from 50.7.178.102 table eth0:4_if