Tested with v2.2f, default settings.
HFS is on a PC with a public IP. 2 or more devices behind the same router try to access to HFS to get the same file, the first connection is OK but the second one gets response with 503.
Changing any setting in "Limit" does not help.
From the Wireshark log, 2 connections are with the same source IP but different ports (TCP 1024 and 1025).